diff --git a/src/mcp/client/session.py b/src/mcp/client/session.py
index c1cc5b5f..b3041333 100644
--- a/src/mcp/client/session.py
+++ b/src/mcp/client/session.py
@@ -219,14 +219,19 @@ async def unsubscribe_resource(self, uri: AnyUrl) -> types.EmptyResult:
         )
 
     async def call_tool(
-        self, name: str, arguments: dict | None = None
+        self,
+        name: str,
+        arguments: dict | None = None,
+        request_id: types.CustomRequestId | None = None,
     ) -> types.CallToolResult:
         """Send a tools/call request."""
         return await self.send_request(
             types.ClientRequest(
                 types.CallToolRequest(
                     method="tools/call",
-                    params=types.CallToolRequestParams(name=name, arguments=arguments),
+                    params=types.CallToolRequestParams(
+                        name=name, arguments=arguments, request_id=request_id
+                    ),
                 )
             ),
             types.CallToolResult,
@@ -244,14 +249,19 @@ async def list_prompts(self) -> types.ListPromptsResult:
         )
 
     async def get_prompt(
-        self, name: str, arguments: dict[str, str] | None = None
+        self,
+        name: str,
+        arguments: dict[str, str] | None = None,
+        request_id: types.CustomRequestId | None = None,
     ) -> types.GetPromptResult:
         """Send a prompts/get request."""
         return await self.send_request(
             types.ClientRequest(
                 types.GetPromptRequest(
                     method="prompts/get",
-                    params=types.GetPromptRequestParams(name=name, arguments=arguments),
+                    params=types.GetPromptRequestParams(
+                        name=name, arguments=arguments, request_id=request_id
+                    ),
                 )
             ),
             types.GetPromptResult,
diff --git a/src/mcp/shared/session.py b/src/mcp/shared/session.py
index 3d3988ce..2afb2433 100644
--- a/src/mcp/shared/session.py
+++ b/src/mcp/shared/session.py
@@ -21,6 +21,7 @@
     JSONRPCNotification,
     JSONRPCRequest,
     JSONRPCResponse,
+    RequestId,
     RequestParams,
     ServerNotification,
     ServerRequest,
@@ -36,8 +37,6 @@
     "ReceiveNotificationT", ClientNotification, ServerNotification
 )
 
-RequestId = str | int
-
 
 class RequestResponder(Generic[ReceiveRequestT, SendResultT]):
     """Handles responding to MCP requests and manages request lifecycle.
@@ -208,9 +207,12 @@ async def send_request(
         Do not use this method to emit notifications! Use send_notification()
         instead.
         """
-
-        request_id = self._request_id
-        self._request_id = request_id + 1
+        params = request.root.params
+        if params is not None and params.request_id is not None:
+            request_id = params.request_id
+        else:
+            request_id = self._request_id
+            self._request_id = request_id + 1
 
         response_stream, response_stream_reader = anyio.create_memory_object_stream[
             JSONRPCResponse | JSONRPCError
@@ -297,9 +299,11 @@ async def _receive_loop(self) -> None:
 
                     responder = RequestResponder(
                         request_id=message.root.id,
-                        request_meta=validated_request.root.params.meta
-                        if validated_request.root.params
-                        else None,
+                        request_meta=(
+                            validated_request.root.params.meta
+                            if validated_request.root.params
+                            else None
+                        ),
                         request=validated_request,
                         session=self,
                         on_complete=lambda r: self._in_flight.pop(r.request_id, None),
diff --git a/src/mcp/types.py b/src/mcp/types.py
index 7d867bd3..5cd01b83 100644
--- a/src/mcp/types.py
+++ b/src/mcp/types.py
@@ -34,7 +34,9 @@
 ProgressToken = str | int
 Cursor = str
 Role = Literal["user", "assistant"]
-RequestId = str | int
+CustomRequestId = str
+AutomaticRequestId = int
+RequestId = CustomRequestId | AutomaticRequestId
 AnyFunction: TypeAlias = Callable[..., Any]
 
 
@@ -51,6 +53,7 @@ class Meta(BaseModel):
         model_config = ConfigDict(extra="allow")
 
     meta: Meta | None = Field(alias="_meta", default=None)
+    request_id: CustomRequestId | None = Field(default=None)
 
 
 class NotificationParams(BaseModel):