docs(go/plugins/mcp): update mcp samples in README (#3629)

Author: hugoaguirre

go/plugins/mcp/README.md

@@ -1,6 +1,8 @@
 # Genkit MCP Plugin
 
-Model Context Protocol (MCP) integration for Go Genkit - connect to MCP servers and expose Genkit tools as MCP servers.
+Model Context Protocol (MCP) integration for Go Genkit
+
+Connect to MCP servers and expose Genkit tools as MCP servers.
 
 ## GenkitMCPClient - Single Server Connection
 
@@ -10,52 +12,40 @@ Connect to and use tools/prompts from a single MCP server:
 package main
 
 import (
-    "context"
-    "log"
-    
-    "github.com/firebase/genkit/go/genkit"
-    "github.com/firebase/genkit/go/plugins/mcp"
+  "context"
+  "log"
+
+  "github.com/firebase/genkit/go/genkit"
+  "github.com/firebase/genkit/go/plugins/mcp"
 )
 
 func main() {
-    ctx := context.Background()
-    g, _ := genkit.Init(ctx)
-    
-    // Connect to the MCP everything server
-    client, err := mcp.NewGenkitMCPClient(mcp.MCPClientOptions{
-        Name: "everything-server",
-        Stdio: &mcp.StdioConfig{
-            Command: "npx",
-            Args: []string{"-y", "@modelcontextprotocol/server-everything"},
-        },
-    })
-    if err != nil {
-        log.Fatal(err)
-    }
-    
-    // Get specific tools from the everything server
-    echoTool, err := client.GetTool(ctx, g, "echo")
-    if err != nil {
-        log.Fatal(err)
-    }
-    
-    addTool, err := client.GetTool(ctx, g, "add")
-    if err != nil {
-        log.Fatal(err)
-    }
-    
-    // Get specific prompts from the everything server
-    simplePrompt, err := client.GetPrompt(ctx, g, "simple_prompt")
-    if err != nil {
-        log.Fatal(err)
-    }
-    
-    // Get all available tools
-    tools, err := client.GetActiveTools(ctx, g)
-    if err != nil {
-        log.Fatal(err)
-    }
-    
+  ctx := context.Background()
+  g := genkit.Init(ctx)
+
+  // Connect to the MCP everything server
+  client, err := mcp.NewGenkitMCPClient(mcp.MCPClientOptions{
+    Name: "everything-server",
+    Stdio: &mcp.StdioConfig{
+      Command: "npx",
+      Args:    []string{"-y", "@modelcontextprotocol/server-everything"},
+    },
+  })
+  if err != nil {
+    log.Fatal(err)
+  }
+
+  // Get specific prompts from the everything server
+  simplePrompt, err := client.GetPrompt(ctx, g, "simple-prompt", nil)
+  if err != nil {
+    log.Fatal(err)
+  }
+
+  // Get all available tools
+  tools, err := client.GetActiveTools(ctx, g)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -69,15 +59,15 @@ package main
 import (
     "context"
     "log"
-    
+
     "github.com/firebase/genkit/go/genkit"
     "github.com/firebase/genkit/go/plugins/mcp"
 )
 
 func main() {
     ctx := context.Background()
     g, _ := genkit.Init(ctx)
-    
+
     // Create manager with multiple servers
     manager, err := mcp.NewMCPManager(mcp.MCPManagerOptions{
         Name: "my-app",
@@ -101,7 +91,7 @@ func main() {
     if err != nil {
         log.Fatal(err)
     }
-    
+
     // Connect to new server at runtime
     err = manager.ConnectServer(ctx, "weather", mcp.MCPClientOptions{
         Name: "weather-server",
@@ -113,14 +103,14 @@ func main() {
     if err != nil {
         log.Fatal(err)
     }
-    
+
     // Temporarily disable/enable servers
     manager.DisableServer("filesystem")
     manager.EnableServer("filesystem")
-    
+
     // Disconnect server
     manager.DisconnectServer("weather")
-    
+
     // Get tools from all active servers
     tools, err := manager.GetActiveTools(ctx, g)
     if err != nil {
@@ -137,48 +127,72 @@ Turn your Genkit app into an MCP server:
 package main
 
 import (
-    "context"
-    "log"
-    
-    "github.com/firebase/genkit/go/genkit"
-    "github.com/firebase/genkit/go/plugins/mcp"
-    "github.com/firebase/genkit/go/ai"
+  "context"
+  "log"
+
+  "github.com/firebase/genkit/go/genkit"
+  "github.com/firebase/genkit/go/plugins/mcp"
 )
 
 func main() {
-    ctx := context.Background()
-    g, _ := genkit.Init(ctx)
-    
-    // Define some tools
-    addTool := genkit.DefineTool(g, "add", "Add two numbers",
-        func(ctx *ai.ToolContext, input struct{A, B int}) (int, error) {
-            return input.A + input.B, nil
-        })
-    
-    multiplyTool := genkit.DefineTool(g, "multiply", "Multiply two numbers",
-        func(ctx *ai.ToolContext, input struct{X, Y int}) (int, error) {
-            return input.X * input.Y, nil
-        })
-    
-    // Option 1: Auto-expose all tools
-    server := mcp.NewMCPServer(g, mcp.MCPServerOptions{
-        Name:    "genkit-calculator",
-        Version: "1.0.0",
-    })
-    
-    // Option 2: Expose specific tools only
-    server = mcp.NewMCPServer(g, mcp.MCPServerOptions{
-        Name:    "genkit-calculator", 
-        Version: "1.0.0",
-        Tools:   []ai.Tool{addTool, multiplyTool},
-    })
-    
-    // Start MCP server
-    log.Println("Starting MCP server...")
-    if err := server.ServeStdio(ctx); err != nil {
-        log.Fatal(err)
-    }
+  ctx := context.Background()
+  g := genkit.Init(ctx)
+
+  // Create a host with multiple servers
+  host, err := mcp.NewMCPHost(g, mcp.MCPHostOptions{
+    Name: "my-app",
+    MCPServers: []mcp.MCPServerConfig{
+      {
+        Name: "everything-server",
+        Config: mcp.MCPClientOptions{
+          Name: "everything-server",
+          Stdio: &mcp.StdioConfig{
+            Command: "npx",
+            Args:    []string{"-y", "@modelcontextprotocol/server-everything"},
+          },
+        },
+      },
+      {
+        Name: "fs-server",
+        Config: mcp.MCPClientOptions{
+          Name: "fs-server",
+          Stdio: &mcp.StdioConfig{
+            Command: "npx",
+            Args:    []string{"@modelcontextprotocol/server-filesystem", "/tmp"},
+          },
+        },
+      },
+    },
+  })
+  if err != nil {
+    log.Fatal(err)
+  }
+
+  // Connect to new server at runtime
+  err = host.Connect(ctx, g, "weather", mcp.MCPClientOptions{
+    Name: "weather-server",
+    Stdio: &mcp.StdioConfig{
+      Command: "python",
+      Args:    []string{"weather_server.py"},
+    },
+  })
+  if err != nil {
+    log.Fatal(err)
+  }
+
+  // Reconnect server
+  host.Reconnect(ctx, "fs-server")
+
+  // Disconnect server
+  host.Disconnect(ctx, "weather")
+
+  // Get tools from all active servers
+  tools, err := host.GetActiveTools(ctx, g)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
+
 ```
 
 ## Testing Your Server
@@ -194,6 +208,7 @@ npx @modelcontextprotocol/inspector go run main.go
 ## Transport Options
 
 ### Stdio (Standard)
+
 ```go
 Stdio: &mcp.StdioConfig{
     Command: "uvx",
@@ -203,6 +218,7 @@ Stdio: &mcp.StdioConfig{
 ```
 
 ### SSE (Web clients)
+
 ```go
 SSE: &mcp.SSEConfig{
     BaseURL: "http://localhost:3000/sse",