internal/mcp: export the Transport interface; add a Server example

Export the Transport interface, as there's no reason users shouldn't be
able to define their own transports: they are just bidirectional
streams.

Also, add a godoc example for basic Server usage.

Finally, remove some TODOs that existed due to a bad merge: they are
related to the (as yet unsubmitted) streamable HTTP transport.

Change-Id: Id669793fc80630e667d50611fe2876d09125a025
Reviewed-on: https://go-review.googlesource.com/c/tools/+/668675
TryBot-Bypass: Robert Findley <rfindley@google.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>

mcp/example_test.go

@@ -0,0 +1,53 @@
+// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package mcp_test
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+)
+
+type SayHiParams struct {
+	Name string `json:"name" mcp:"the name to say hi to"`
+}
+
+func SayHi(ctx context.Context, cc *mcp.ClientConnection, params *SayHiParams) ([]mcp.Content, error) {
+	return []mcp.Content{
+		mcp.TextContent{Text: "Hi " + params.Name},
+	}, nil
+}
+
+func ExampleServer() {
+	ctx := context.Background()
+	clientTransport, serverTransport := mcp.NewLocalTransport()
+
+	server := mcp.NewServer("greeter", "v0.0.1", nil)
+	server.AddTools(mcp.MakeTool("greet", "say hi", SayHi))
+
+	clientConnection, err := server.Connect(ctx, serverTransport, nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	client := mcp.NewClient("client", "v0.0.1", nil)
+	serverConnection, err := client.Connect(ctx, clientTransport, nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	content, err := serverConnection.CallTool(ctx, "greet", SayHiParams{Name: "user"})
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(content[0].(mcp.TextContent).Text)
+
+	serverConnection.Close()
+	clientConnection.Wait()
+
+	// Output: Hi user
+}