diff --git a/.gitignore b/.gitignore
index 12723e9..f8b6f7b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,4 @@ node_modules
 .phpunit.result.cache
 docs/.vitepress/dist
 docs/.vitepress/cache
+.idea/*
diff --git a/src/Endpoint/CollectionAction.php b/src/Endpoint/CollectionAction.php
index 0310976..5deec0f 100644
--- a/src/Endpoint/CollectionAction.php
+++ b/src/Endpoint/CollectionAction.php
@@ -6,17 +6,21 @@
 use Nyholm\Psr7\Response;
 use Psr\Http\Message\ResponseInterface;
 use Tobyz\JsonApiServer\Context;
+use Tobyz\JsonApiServer\Endpoint\Concerns\BuildsOpenApiPaths;
 use Tobyz\JsonApiServer\Exception\ForbiddenException;
 use Tobyz\JsonApiServer\Exception\MethodNotAllowedException;
 use Tobyz\JsonApiServer\OpenApi\OpenApiPathsProvider;
 use Tobyz\JsonApiServer\Resource\Collection;
 use Tobyz\JsonApiServer\Schema\Concerns\HasDescription;
+use Tobyz\JsonApiServer\Schema\Concerns\HasSummary;
 use Tobyz\JsonApiServer\Schema\Concerns\HasVisibility;
 
 class CollectionAction implements Endpoint, OpenApiPathsProvider
 {
     use HasVisibility;
+    use HasSummary;
     use HasDescription;
+    use BuildsOpenApiPaths;
 
     public string $method = 'POST';
 
@@ -52,9 +56,7 @@ public function handle(Context $context): ?ResponseInterface
             throw new ForbiddenException();
         }
 
-        ($this->handler)($context);
-
-        return new Response(204);
+        return ($this->handler)($context) ?? new Response(204);
     }
 
     public function getOpenApiPaths(Collection $collection): array
@@ -62,10 +64,17 @@ public function getOpenApiPaths(Collection $collection): array
         return [
             "/{$collection->name()}/$this->name" => [
                 'post' => [
+                    'summary' => $this->getSummary(),
                     'description' => $this->getDescription(),
                     'tags' => [$collection->name()],
                     'responses' => [
-                        '204' => [],
+                        '204' => [
+                            'description' => 'No Content',
+                        ],
+                        '400' => $this->buildBadRequestErrorResponse(),
+                        '401' => $this->buildUnauthorizedErrorResponse(),
+                        '403' => $this->buildForbiddenErrorResponse(),
+                        '500' => $this->buildInternalServerErrorResponse(),
                     ],
                 ],
             ],
diff --git a/src/Endpoint/Concerns/BuildsOpenApiPaths.php b/src/Endpoint/Concerns/BuildsOpenApiPaths.php
index 65cf5a1..ae28af6 100644
--- a/src/Endpoint/Concerns/BuildsOpenApiPaths.php
+++ b/src/Endpoint/Concerns/BuildsOpenApiPaths.php
@@ -2,12 +2,27 @@
 
 namespace Tobyz\JsonApiServer\Endpoint\Concerns;
 
+use ReflectionException;
+use ReflectionFunction;
+use Tobyz\JsonApiServer\Endpoint\Index;
 use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Resource\Collection;
+use Tobyz\JsonApiServer\Resource\Resource;
+use Tobyz\JsonApiServer\Schema\Field\Field;
+use Tobyz\JsonApiServer\Schema\Field\Relationship;
+use Tobyz\JsonApiServer\Schema\Filter;
 
 trait BuildsOpenApiPaths
 {
-    private function buildOpenApiContent(array $resources, bool $multiple = false): array
-    {
+    private function buildOpenApiContent(
+        string $name,
+        array $resources,
+        bool $multiple = false,
+        bool $included = true,
+        bool $links = false,
+        bool $countable = false,
+        bool $paginatable = false,
+    ): array {
         $item = count($resources) === 1 ? $resources[0] : ['oneOf' => $resources];
 
         return [
@@ -15,8 +30,271 @@ private function buildOpenApiContent(array $resources, bool $multiple = false):
                 'schema' => [
                     'type' => 'object',
                     'required' => ['data'],
-                    'properties' => [
+                    'properties' => array_filter([
+                        'links' => $links ? $this->buildLinksObject($name) : [],
                         'data' => $multiple ? ['type' => 'array', 'items' => $item] : $item,
+                        'included' => $included ? ['type' => 'array'] : [],
+                        'meta' => $this->buildMetaObject($countable, $paginatable),
+                    ]),
+                ],
+            ],
+        ];
+    }
+
+    private function buildLinksObject(string $name): array
+    {
+        // @todo: maybe pull in the API or Context to return a server name?
+        $baseUri = sprintf('https://{server}/%s', $name);
+        $defaultQuery = ['page[limit]' => 10];
+
+        $links = [
+            'self' => ['page[offset]' => 2],
+            'first' => ['page[offset]' => 1],
+            'prev' => ['page[offset]' => 1],
+            'next' => ['page[offset]' => 3],
+            'last' => ['page[offset]' => 10],
+        ];
+
+        foreach ($links as $key => $params) {
+            $params = $params + $defaultQuery;
+
+            $query = implode(
+                '&',
+                array_map(
+                    fn($k, $v) => $k . '=' . urlencode($v),
+                    array_keys($params),
+                    $params,
+                )
+            );
+
+            $links[$key] = sprintf('%s/%s', $baseUri, $query);
+        }
+
+        return [
+            'type' => 'object',
+            'properties' => array_map(function (string $uri) {
+                return [
+                    'type' => 'string',
+                    'example' => $uri,
+                ];
+            }, $links),
+        ];
+    }
+
+    private function buildMetaObject(bool $countable, bool $paginatable): array
+    {
+        if (!($countable || $paginatable)) {
+            return [];
+        }
+
+        return [
+            'type' => 'object',
+            'properties' => [
+                'page' => [
+                    'type' => 'object',
+                    'properties' => array_filter([
+                        'total' => $countable ? ['type' => 'integer'] : [],
+                        'limit' => $paginatable ? ['type' => 'integer'] : [],
+                        'offset' => $paginatable ? ['type' => 'integer'] : [],
+                    ]),
+                ],
+            ],
+        ];
+    }
+
+    /**
+     * @throws ReflectionException
+     */
+    private function buildOpenApiParameters(Collection $collection): array
+    {
+        // @todo: fix this
+        assert($collection instanceof Resource);
+
+        $parameters = [
+            $this->buildIncludeParameter($collection),
+            ...$this->buildFilterParameters($collection),
+            ...$this->buildPaginatableParameters(),
+        ];
+
+        return array_values(array_filter($parameters));
+    }
+
+    private function buildIncludeParameter(Resource $resource): array
+    {
+        $relationshipNames = array_map(
+            fn(Relationship $relationship) => $relationship->name,
+            array_filter(
+                $resource->fields(),
+                fn(Field $field) => $field instanceof Relationship && $field->includable,
+            ),
+        );
+
+        if (empty($relationshipNames)) {
+            return [];
+        }
+
+        $includes = implode(', ', $relationshipNames);
+
+        return [
+            'name' => 'include',
+            'in' => 'query',
+            'description' => "Available include parameters: {$includes}.",
+            'schema' => [
+                'type' => 'string',
+            ],
+        ];
+    }
+
+
+    private function buildFilterParameters(Resource $resource): array
+    {
+        if (!$this instanceof Index) {
+            return [];
+        }
+
+        return array_map(function (Filter $filter) {
+            return [
+                'name' => "filter[{$filter->name}]",
+                'in' => 'query',
+                'description' => $filter->getDescription(),
+                'schema' => [
+                    'type' => 'string',
+                ],
+            ];
+        }, $resource->filters());
+    }
+
+    /**
+     * @throws ReflectionException
+     */
+    private function buildPaginatableParameters(): array
+    {
+        if (property_exists($this, 'paginationResolver')) {
+            $resolver = $this->paginationResolver;
+            $reflection = new ReflectionFunction($resolver);
+
+            if ($reflection->getNumberOfRequiredParameters() > 0) {
+                return [
+                    [
+                        'name' => 'page[limit]',
+                        'in' => 'query',
+                        'description' => "The limit pagination field.",
+                        'schema' => [
+                            'type' => 'number',
+                        ],
+                    ],
+                    [
+                        'name' => 'page[offset]',
+                        'in' => 'query',
+                        'description' => "The offset pagination field.",
+                        'schema' => [
+                            'type' => 'number',
+                        ],
+                    ],
+                ];
+            }
+        }
+
+        return [];
+    }
+
+    public function buildBadRequestErrorResponse(): array
+    {
+        return $this->buildErrorResponse(
+            'A bad request.',
+            400,
+            'Bad Request',
+            'Please try again with a valid request.',
+        );
+    }
+
+    public function buildUnauthorizedErrorResponse(): array
+    {
+        return $this->buildErrorResponse(
+            'An unauthorised error.',
+            401,
+            'Unauthorized',
+            'Please login and try again.',
+        );
+    }
+
+    public function buildForbiddenErrorResponse(): array
+    {
+        return $this->buildErrorResponse(
+            'A forbidden error.',
+            403,
+            'Forbidden',
+        );
+    }
+
+    public function buildNotFoundErrorResponse(): array
+    {
+        return $this->buildErrorResponse(
+            'A bad request.',
+            404,
+            'Not Found',
+            'The requested resource could not be found.',
+        );
+    }
+
+    public function buildInternalServerErrorResponse(): array
+    {
+        return $this->buildErrorResponse(
+            'A bad request.',
+            500,
+            'Internal Server Error',
+            'Please try again later.',
+        );
+    }
+
+    public function buildErrorResponse(string $description, int $status, string $title, ?string $detail = null): array
+    {
+        return [
+            'description' => $description,
+            'content' => [
+                JsonApi::MEDIA_TYPE => [
+                    'schema' => [
+                        'type' => 'object',
+                        'properties' => [
+                            'errors' => [
+                                'type' => 'array',
+                                'items' => [
+                                    'type' => 'object',
+                                    'required' => [
+                                        'status',
+                                        'title',
+                                    ],
+                                    'properties' => array_filter([
+                                        'status' => [
+                                            'type' => 'string',
+                                            'example' => (string)$status,
+                                        ],
+                                        'title' => [
+                                            'type' => 'string',
+                                            'example' => $title,
+                                        ],
+                                        'detail' => [
+                                            'type' => 'string',
+                                            'example' => $detail,
+                                        ],
+                                        'source' => [
+                                            'type' => 'object',
+                                            'properties' => [
+                                                'pointer' => [
+                                                    'type' => 'string',
+                                                ],
+                                                'parameter' => [
+                                                    'type' => 'string',
+                                                ],
+                                                'header' => [
+                                                    'type' => 'string',
+                                                ],
+                                            ],
+                                        ],
+                                    ]),
+                                ],
+                            ],
+                        ],
                     ],
                 ],
             ],
diff --git a/src/Endpoint/Concerns/SavesData.php b/src/Endpoint/Concerns/SavesData.php
index 6dbf534..719f74c 100644
--- a/src/Endpoint/Concerns/SavesData.php
+++ b/src/Endpoint/Concerns/SavesData.php
@@ -176,7 +176,7 @@ private function assertDataValid(Context $context, array $data, bool $validateAl
         foreach ($context->fields($context->resource) as $field) {
             $empty = !has_value($data, $field);
 
-            if ($empty && (!$field->required || !$validateAll)) {
+            if ($empty && (!$field->isRequired($context) || !$validateAll)) {
                 continue;
             }
 
@@ -187,7 +187,7 @@ private function assertDataValid(Context $context, array $data, bool $validateAl
                 ];
             };
 
-            if ($empty && $field->required) {
+            if ($empty && $field->isRequired($context)) {
                 $fail('field is required');
             } else {
                 $field->validateValue(get_value($data, $field), $fail, $context->withField($field));
diff --git a/src/Endpoint/Create.php b/src/Endpoint/Create.php
index 0ba8a1c..8d6aaea 100644
--- a/src/Endpoint/Create.php
+++ b/src/Endpoint/Create.php
@@ -14,6 +14,7 @@
 use Tobyz\JsonApiServer\Resource\Collection;
 use Tobyz\JsonApiServer\Resource\Creatable;
 use Tobyz\JsonApiServer\Schema\Concerns\HasDescription;
+use Tobyz\JsonApiServer\Schema\Concerns\HasSummary;
 use Tobyz\JsonApiServer\Schema\Concerns\HasVisibility;
 
 use function Tobyz\JsonApiServer\has_value;
@@ -25,6 +26,7 @@ class Create implements Endpoint, OpenApiPathsProvider
     use HasVisibility;
     use SavesData;
     use ShowsResources;
+    use HasSummary;
     use HasDescription;
     use BuildsOpenApiPaths;
 
@@ -109,11 +111,14 @@ public function getOpenApiPaths(Collection $collection): array
         return [
             "/{$collection->name()}" => [
                 'post' => [
+                    'summary' => $this->getSummary(),
                     'description' => $this->getDescription(),
                     'tags' => [$collection->name()],
+                    'parameters' => $this->buildOpenApiParameters($collection),
                     'requestBody' => [
                         'required' => true,
                         'content' => $this->buildOpenApiContent(
+                            $collection->name(),
                             array_map(
                                 fn($resource) => [
                                     '$ref' => "#/components/schemas/{$resource}Create",
@@ -124,13 +129,20 @@ public function getOpenApiPaths(Collection $collection): array
                     ],
                     'responses' => [
                         '200' => [
+                            'description' => 'Resource created successfully.',
                             'content' => $this->buildOpenApiContent(
+                                $collection->name(),
                                 array_map(
                                     fn($resource) => ['$ref' => "#/components/schemas/$resource"],
                                     $collection->resources(),
                                 ),
                             ),
                         ],
+                        '400' => $this->buildBadRequestErrorResponse(),
+                        '401' => $this->buildUnauthorizedErrorResponse(),
+                        '403' => $this->buildForbiddenErrorResponse(),
+                        '404' => $this->buildNotFoundErrorResponse(),
+                        '500' => $this->buildInternalServerErrorResponse(),
                     ],
                 ],
             ],
diff --git a/src/Endpoint/Delete.php b/src/Endpoint/Delete.php
index f8b20c5..a55eb16 100644
--- a/src/Endpoint/Delete.php
+++ b/src/Endpoint/Delete.php
@@ -6,6 +6,7 @@
 use Psr\Http\Message\ResponseInterface;
 use RuntimeException;
 use Tobyz\JsonApiServer\Context;
+use Tobyz\JsonApiServer\Endpoint\Concerns\BuildsOpenApiPaths;
 use Tobyz\JsonApiServer\Endpoint\Concerns\FindsResources;
 use Tobyz\JsonApiServer\Exception\ForbiddenException;
 use Tobyz\JsonApiServer\Exception\MethodNotAllowedException;
@@ -14,6 +15,7 @@
 use Tobyz\JsonApiServer\Resource\Deletable;
 use Tobyz\JsonApiServer\Schema\Concerns\HasDescription;
 use Tobyz\JsonApiServer\Schema\Concerns\HasMeta;
+use Tobyz\JsonApiServer\Schema\Concerns\HasSummary;
 use Tobyz\JsonApiServer\Schema\Concerns\HasVisibility;
 
 use function Tobyz\JsonApiServer\json_api_response;
@@ -23,7 +25,9 @@ class Delete implements Endpoint, OpenApiPathsProvider
     use HasMeta;
     use HasVisibility;
     use FindsResources;
+    use HasSummary;
     use HasDescription;
+    use BuildsOpenApiPaths;
 
     public static function make(): static
     {
@@ -72,6 +76,7 @@ public function getOpenApiPaths(Collection $collection): array
         return [
             "/{$collection->name()}/{id}" => [
                 'delete' => [
+                    'summary' => $this->getSummary(),
                     'description' => $this->getDescription(),
                     'tags' => [$collection->name()],
                     'parameters' => [
@@ -83,7 +88,14 @@ public function getOpenApiPaths(Collection $collection): array
                         ],
                     ],
                     'responses' => [
-                        '204' => [],
+                        '204' => [
+                            'description' => 'No Content',
+                        ],
+                        '400' => $this->buildBadRequestErrorResponse(),
+                        '401' => $this->buildUnauthorizedErrorResponse(),
+                        '403' => $this->buildForbiddenErrorResponse(),
+                        '404' => $this->buildNotFoundErrorResponse(),
+                        '500' => $this->buildInternalServerErrorResponse(),
                     ],
                 ],
             ],
diff --git a/src/Endpoint/Index.php b/src/Endpoint/Index.php
index 32523ef..5616895 100644
--- a/src/Endpoint/Index.php
+++ b/src/Endpoint/Index.php
@@ -4,6 +4,7 @@
 
 use Closure;
 use Psr\Http\Message\ResponseInterface as Response;
+use ReflectionException;
 use RuntimeException;
 use Tobyz\JsonApiServer\Context;
 use Tobyz\JsonApiServer\Endpoint\Concerns\BuildsOpenApiPaths;
@@ -19,6 +20,7 @@
 use Tobyz\JsonApiServer\Resource\Listable;
 use Tobyz\JsonApiServer\Schema\Concerns\HasDescription;
 use Tobyz\JsonApiServer\Schema\Concerns\HasMeta;
+use Tobyz\JsonApiServer\Schema\Concerns\HasSummary;
 use Tobyz\JsonApiServer\Schema\Concerns\HasVisibility;
 use Tobyz\JsonApiServer\Serializer;
 
@@ -31,6 +33,7 @@ class Index implements Endpoint, OpenApiPathsProvider
     use HasMeta;
     use HasVisibility;
     use IncludesData;
+    use HasSummary;
     use HasDescription;
     use BuildsOpenApiPaths;
 
@@ -173,23 +176,37 @@ private function applyFilters($query, Context $context): void
         }
     }
 
+    /**
+     * @throws ReflectionException
+     */
     public function getOpenApiPaths(Collection $collection): array
     {
         return [
             "/{$collection->name()}" => [
                 'get' => [
+                    'summary' => $this->getSummary(),
                     'description' => $this->getDescription(),
                     'tags' => [$collection->name()],
+                    'parameters' => $this->buildOpenApiParameters($collection),
                     'responses' => [
                         '200' => [
+                            'description' => 'Successful list all response.',
                             'content' => $this->buildOpenApiContent(
+                                $collection->name(),
                                 array_map(
                                     fn($resource) => ['$ref' => "#/components/schemas/$resource"],
                                     $collection->resources(),
                                 ),
                                 multiple: true,
+                                links: true,
+                                countable: true,
+                                paginatable: true,
                             ),
                         ],
+                        '400' => $this->buildBadRequestErrorResponse(),
+                        '401' => $this->buildUnauthorizedErrorResponse(),
+                        '403' => $this->buildForbiddenErrorResponse(),
+                        '500' => $this->buildInternalServerErrorResponse(),
                     ],
                 ],
             ],
diff --git a/src/Endpoint/ResourceAction.php b/src/Endpoint/ResourceAction.php
index df02cff..e5e9468 100644
--- a/src/Endpoint/ResourceAction.php
+++ b/src/Endpoint/ResourceAction.php
@@ -13,6 +13,7 @@
 use Tobyz\JsonApiServer\OpenApi\OpenApiPathsProvider;
 use Tobyz\JsonApiServer\Resource\Collection;
 use Tobyz\JsonApiServer\Schema\Concerns\HasDescription;
+use Tobyz\JsonApiServer\Schema\Concerns\HasSummary;
 use Tobyz\JsonApiServer\Schema\Concerns\HasVisibility;
 
 use function Tobyz\JsonApiServer\json_api_response;
@@ -20,6 +21,7 @@
 class ResourceAction implements Endpoint, OpenApiPathsProvider
 {
     use HasVisibility;
+    use HasSummary;
     use HasDescription;
     use FindsResources;
     use ShowsResources;
@@ -75,6 +77,7 @@ public function getOpenApiPaths(Collection $collection): array
         return [
             "/{$collection->name()}/{id}/{$this->name}" => [
                 strtolower($this->method) => [
+                    'summary' => $this->getSummary(),
                     'description' => $this->getDescription(),
                     'tags' => [$collection->name()],
                     'parameters' => [
@@ -87,13 +90,20 @@ public function getOpenApiPaths(Collection $collection): array
                     ],
                     'responses' => [
                         '200' => [
+                            'description' => 'Successful custom action response.',
                             'content' => $this->buildOpenApiContent(
+                                $collection->name(),
                                 array_map(
                                     fn($resource) => ['$ref' => "#/components/schemas/$resource"],
                                     $collection->resources(),
                                 ),
                             ),
                         ],
+                        '400' => $this->buildBadRequestErrorResponse(),
+                        '401' => $this->buildUnauthorizedErrorResponse(),
+                        '403' => $this->buildForbiddenErrorResponse(),
+                        '404' => $this->buildNotFoundErrorResponse(),
+                        '500' => $this->buildInternalServerErrorResponse(),
                     ],
                 ],
             ],
diff --git a/src/Endpoint/Show.php b/src/Endpoint/Show.php
index 6a9aca6..d6afb4c 100644
--- a/src/Endpoint/Show.php
+++ b/src/Endpoint/Show.php
@@ -12,6 +12,7 @@
 use Tobyz\JsonApiServer\OpenApi\OpenApiPathsProvider;
 use Tobyz\JsonApiServer\Resource\Collection;
 use Tobyz\JsonApiServer\Schema\Concerns\HasDescription;
+use Tobyz\JsonApiServer\Schema\Concerns\HasSummary;
 use Tobyz\JsonApiServer\Schema\Concerns\HasVisibility;
 
 use function Tobyz\JsonApiServer\json_api_response;
@@ -21,6 +22,7 @@ class Show implements Endpoint, OpenApiPathsProvider
     use HasVisibility;
     use FindsResources;
     use ShowsResources;
+    use HasSummary;
     use HasDescription;
     use BuildsOpenApiPaths;
 
@@ -52,28 +54,41 @@ public function handle(Context $context): ?ResponseInterface
 
     public function getOpenApiPaths(Collection $collection): array
     {
+        $parameters = array_merge(
+            [
+                [
+                    'name' => 'id',
+                    'in' => 'path',
+                    'required' => true,
+                    'schema' => ['type' => 'string'],
+                ],
+            ],
+            $this->buildOpenApiParameters($collection)
+        );
+
         return [
             "/{$collection->name()}/{id}" => [
                 'get' => [
+                    'summary' => $this->getSummary(),
                     'description' => $this->getDescription(),
                     'tags' => [$collection->name()],
-                    'parameters' => [
-                        [
-                            'name' => 'id',
-                            'in' => 'path',
-                            'required' => true,
-                            'schema' => ['type' => 'string'],
-                        ],
-                    ],
+                    'parameters' => $parameters,
                     'responses' => [
                         '200' => [
+                            'description' => 'Successful show response.',
                             'content' => $this->buildOpenApiContent(
+                                $collection->name(),
                                 array_map(
                                     fn($resource) => ['$ref' => "#/components/schemas/$resource"],
                                     $collection->resources(),
                                 ),
                             ),
                         ],
+                        '400' => $this->buildBadRequestErrorResponse(),
+                        '401' => $this->buildUnauthorizedErrorResponse(),
+                        '403' => $this->buildForbiddenErrorResponse(),
+                        '404' => $this->buildNotFoundErrorResponse(),
+                        '500' => $this->buildInternalServerErrorResponse(),
                     ],
                 ],
             ],
diff --git a/src/Endpoint/Update.php b/src/Endpoint/Update.php
index 838fd8f..3680edb 100644
--- a/src/Endpoint/Update.php
+++ b/src/Endpoint/Update.php
@@ -15,6 +15,7 @@
 use Tobyz\JsonApiServer\Resource\Collection;
 use Tobyz\JsonApiServer\Resource\Updatable;
 use Tobyz\JsonApiServer\Schema\Concerns\HasDescription;
+use Tobyz\JsonApiServer\Schema\Concerns\HasSummary;
 use Tobyz\JsonApiServer\Schema\Concerns\HasVisibility;
 
 use function Tobyz\JsonApiServer\json_api_response;
@@ -25,6 +26,7 @@ class Update implements Endpoint, OpenApiPathsProvider
     use FindsResources;
     use SavesData;
     use ShowsResources;
+    use HasSummary;
     use HasDescription;
     use BuildsOpenApiPaths;
 
@@ -82,6 +84,7 @@ public function getOpenApiPaths(Collection $collection): array
         return [
             "/{$collection->name()}/{id}" => [
                 'patch' => [
+                    'summary' => $this->getSummary(),
                     'description' => $this->getDescription(),
                     'tags' => [$collection->name()],
                     'parameters' => [
@@ -95,6 +98,7 @@ public function getOpenApiPaths(Collection $collection): array
                     'requestBody' => [
                         'required' => true,
                         'content' => $this->buildOpenApiContent(
+                            $collection->name(),
                             array_map(
                                 fn($resource) => [
                                     '$ref' => "#/components/schemas/{$resource}Update",
@@ -105,13 +109,20 @@ public function getOpenApiPaths(Collection $collection): array
                     ],
                     'responses' => [
                         '200' => [
+                            'description' => 'Successful update response.',
                             'content' => $this->buildOpenApiContent(
+                                $collection->name(),
                                 array_map(
                                     fn($resource) => ['$ref' => "#/components/schemas/$resource"],
                                     $collection->resources(),
                                 ),
                             ),
                         ],
+                        '400' => $this->buildBadRequestErrorResponse(),
+                        '401' => $this->buildUnauthorizedErrorResponse(),
+                        '403' => $this->buildForbiddenErrorResponse(),
+                        '404' => $this->buildNotFoundErrorResponse(),
+                        '500' => $this->buildInternalServerErrorResponse(),
                     ],
                 ],
             ],
diff --git a/src/OpenApi/Decorator.php b/src/OpenApi/Decorator.php
new file mode 100644
index 0000000..119ed18
--- /dev/null
+++ b/src/OpenApi/Decorator.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Tobyz\JsonApiServer\OpenApi;
+
+abstract class Decorator implements GeneratorInterface
+{
+    public function __construct(protected GeneratorInterface $inner)
+    {
+    }
+}
diff --git a/src/OpenApi/GeneratorInterface.php b/src/OpenApi/GeneratorInterface.php
new file mode 100644
index 0000000..a726636
--- /dev/null
+++ b/src/OpenApi/GeneratorInterface.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Tobyz\JsonApiServer\OpenApi;
+
+use Tobyz\JsonApiServer\JsonApi;
+
+interface GeneratorInterface
+{
+    public function generate(JsonApi $api): array;
+}
diff --git a/src/OpenApi/OpenApiGenerator.php b/src/OpenApi/OpenApiGenerator.php
index ed09e5e..edc19c6 100644
--- a/src/OpenApi/OpenApiGenerator.php
+++ b/src/OpenApi/OpenApiGenerator.php
@@ -7,7 +7,7 @@
 
 use function Tobyz\JsonApiServer\location;
 
-class OpenApiGenerator
+class OpenApiGenerator implements GeneratorInterface
 {
     public function generate(JsonApi $api): array
     {
@@ -46,14 +46,14 @@ public function generate(JsonApi $api): array
 
                 if ($field->writable) {
                     $updateSchema[$location]['properties'][$field->name] = $fieldSchema;
-                    if ($field->required) {
+                    if ($field->isRequired()) {
                         $updateSchema[$location]['required'][] = $field->name;
                     }
                 }
 
-                if ($field->writableOnCreate) {
+                if ($field->writable || $field->writableOnCreate) {
                     $createSchema[$location]['properties'][$field->name] = $fieldSchema;
-                    if ($field->required) {
+                    if ($field->isRequired()) {
                         $createSchema[$location]['required'][] = $field->name;
                     }
                 }
@@ -62,14 +62,16 @@ public function generate(JsonApi $api): array
             $type = $resource->type();
 
             $schemas[$type] = $this->buildSchema($resource, $schema, [
+                'required' => ['id'],
                 'properties' => ['id' => ['type' => 'string', 'readOnly' => true]],
             ]);
 
-            $schemas["{$type}Create"] = $this->buildSchema($resource, $createSchema, [
-                'required' => ['type'],
-            ]);
+            $schemas["{$type}Create"] = $this->buildSchema($resource, $createSchema);
 
-            $schemas["{$type}Update"] = $this->buildSchema($resource, $updateSchema);
+            $schemas["{$type}Update"] = $this->buildSchema($resource, $updateSchema, [
+                'required' => ['type', 'id'],
+                'properties' => ['id' => ['type' => 'string']],
+            ]);
         }
 
         return array_filter([
@@ -88,13 +90,21 @@ public function generate(JsonApi $api): array
 
     private function buildSchema(Resource $resource, array $schema, array $overrides = []): array
     {
+        $hasAttributes = !empty($schema['attributes']);
+        $hasRelationships = !empty($schema['relationships']);
+
         return array_replace_recursive(
             [
                 'type' => 'object',
-                'required' => ['type', 'id'],
+                'required' => array_values(
+                    array_filter([
+                        'type',
+                        $hasAttributes ? 'attributes' : null,
+                        $hasRelationships ? 'relationships' : null,
+                    ])
+                ),
                 'properties' => [
                     'type' => ['type' => 'string', 'const' => $resource->type()],
-                    'id' => ['type' => 'string'],
                     'attributes' => ['type' => 'object'] + ($schema['attributes'] ?? []),
                     'relationships' => ['type' => 'object'] + ($schema['relationships'] ?? []),
                 ],
diff --git a/src/OpenApi/OpenApiPathsProvider.php b/src/OpenApi/OpenApiPathsProvider.php
index b066adf..023ec47 100644
--- a/src/OpenApi/OpenApiPathsProvider.php
+++ b/src/OpenApi/OpenApiPathsProvider.php
@@ -3,6 +3,7 @@
 namespace Tobyz\JsonApiServer\OpenApi;
 
 use Tobyz\JsonApiServer\Resource\Collection;
+use Tobyz\JsonApiServer\Resource\Resource;
 
 interface OpenApiPathsProvider
 {
diff --git a/src/Resource/Paginatable.php b/src/Resource/Paginatable.php
index 6da9d08..8021f21 100644
--- a/src/Resource/Paginatable.php
+++ b/src/Resource/Paginatable.php
@@ -2,12 +2,12 @@
 
 namespace Tobyz\JsonApiServer\Resource;
 
-use Tobyz\JsonApiServer\Pagination\OffsetPagination;
+use Tobyz\JsonApiServer\Pagination\Pagination;
 
 interface Paginatable
 {
     /**
      * Paginate the given query.
      */
-    public function paginate(object $query, OffsetPagination $pagination): void;
+    public function paginate(object $query, Pagination $pagination): void;
 }
diff --git a/src/Schema/Concerns/HasSummary.php b/src/Schema/Concerns/HasSummary.php
new file mode 100644
index 0000000..480af0a
--- /dev/null
+++ b/src/Schema/Concerns/HasSummary.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Tobyz\JsonApiServer\Schema\Concerns;
+
+trait HasSummary
+{
+    protected ?string $summary = null;
+
+    /**
+     * Set the summary of the field for documentation generation.
+     */
+    public function summary(?string $summary): static
+    {
+        $this->summary = $summary;
+
+        return $this;
+    }
+
+    public function getSummary(): ?string
+    {
+        return $this->summary;
+    }
+}
diff --git a/src/Schema/Concerns/SetsValue.php b/src/Schema/Concerns/SetsValue.php
index c6181e5..c334511 100644
--- a/src/Schema/Concerns/SetsValue.php
+++ b/src/Schema/Concerns/SetsValue.php
@@ -11,7 +11,7 @@ trait SetsValue
 {
     public ?Closure $writable = null;
     public ?Closure $writableOnCreate = null;
-    public bool $required = false;
+    public ?Closure $required = null;
     public ?Closure $default = null;
     public ?Closure $deserializer = null;
     public ?Closure $setter = null;
@@ -41,9 +41,9 @@ public function writableOnCreate(?Closure $condition = null): static
     /**
      * Mark this field as required.
      */
-    public function required(bool $required = true): static
+    public function required(?Closure $condition = null): static
     {
-        $this->required = $required;
+        $this->required = $condition ?: fn() => true;
 
         return $this;
     }
@@ -121,6 +121,14 @@ public function isWritableOnCreate(Context $context): bool
             ($this->writableOnCreate && ($this->writableOnCreate)($context->model, $context));
     }
 
+    /**
+     * Check if this field is required.
+     */
+    public function isRequired(): bool
+    {
+        return $this->required && ($this->required)();
+    }
+
     /**
      * Deserialize a JSON value to an internal representation.
      */
diff --git a/src/Schema/Field/Relationship.php b/src/Schema/Field/Relationship.php
index a5e229e..e6b1529 100644
--- a/src/Schema/Field/Relationship.php
+++ b/src/Schema/Field/Relationship.php
@@ -134,7 +134,7 @@ public function getSchema(JsonApi $api): array
             parent::getSchema($api) + [
                 'type' => 'object',
                 'properties' => ['data' => $this->getDataSchema($api)],
-                'required' => $this->required ? ['data'] : [],
+                'required' => $this->isRequired() ? ['data'] : [],
             ];
     }