// 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/google/jsonschema-go/jsonschema" "github.com/modelcontextprotocol/go-sdk/mcp" ) // !+roots func Example_roots() { ctx := context.Background() // Create a client with two roots. c := mcp.NewClient(&mcp.Implementation{Name: "client", Version: "v0.0.1"}, nil) c.AddRoots(&mcp.Root{URI: "file://a"}, &mcp.Root{URI: "file://b"}) // Create a server with a tool that requests roots via the multi round-trip // pattern (SEP-2322): server-to-client requests are no longer sent as // standalone JSON-RPC calls on protocol version >= 2026-07-28. s := mcp.NewServer(&mcp.Implementation{Name: "server", Version: "v0.0.1"}, nil) mcp.AddTool(s, &mcp.Tool{Name: "roots"}, func(_ context.Context, req *mcp.CallToolRequest, _ struct{}) (*mcp.CallToolResult, any, error) { if len(req.Params.InputResponses) == 0 { return &mcp.CallToolResult{ InputRequests: mcp.InputRequestMap{"roots": &mcp.ListRootsParams{}}, }, nil, nil } rootList := req.Params.InputResponses["roots"].(*mcp.ListRootsResult) var roots []string for _, root := range rootList.Roots { roots = append(roots, root.URI) } fmt.Println(roots) return &mcp.CallToolResult{}, nil, nil }) // Connect the server and client... t1, t2 := mcp.NewInMemoryTransports() serverSession, err := s.Connect(ctx, t1, nil) if err != nil { log.Fatal(err) } defer serverSession.Close() clientSession, err := c.Connect(ctx, t2, nil) if err != nil { log.Fatal(err) } defer clientSession.Close() // ...and call the tool. The client's multi round-trip driver fulfils the // embedded roots/list request and retries the call. if _, err := clientSession.CallTool(ctx, &mcp.CallToolParams{Name: "roots"}); err != nil { log.Fatal(err) } // Output: [file://a file://b] } // !-roots // !+sampling func Example_sampling() { ctx := context.Background() // Create a client with a sampling handler. c := mcp.NewClient(&mcp.Implementation{Name: "client", Version: "v0.0.1"}, &mcp.ClientOptions{ CreateMessageHandler: func(_ context.Context, req *mcp.CreateMessageRequest) (*mcp.CreateMessageResult, error) { return &mcp.CreateMessageResult{ Content: &mcp.TextContent{ Text: "would have created a message", }, }, nil }, }) // Connect the server and client... ct, st := mcp.NewInMemoryTransports() // Create a server with a tool that requests sampling via the multi // round-trip pattern (SEP-2322): server-to-client requests are no longer // sent as standalone JSON-RPC calls on protocol version >= 2026-07-28. s := mcp.NewServer(&mcp.Implementation{Name: "server", Version: "v0.0.1"}, nil) mcp.AddTool(s, &mcp.Tool{Name: "sample"}, func(_ context.Context, req *mcp.CallToolRequest, _ struct{}) (*mcp.CallToolResult, any, error) { if len(req.Params.InputResponses) == 0 { return &mcp.CallToolResult{ InputRequests: mcp.InputRequestMap{"msg": &mcp.CreateMessageParams{}}, }, nil, nil } msg := req.Params.InputResponses["msg"].(*mcp.CreateMessageWithToolsResult) return &mcp.CallToolResult{Content: msg.Content}, nil, nil }) session, err := s.Connect(ctx, st, nil) if err != nil { log.Fatal(err) } defer session.Close() clientSession, err := c.Connect(ctx, ct, nil) if err != nil { log.Fatal(err) } res, err := clientSession.CallTool(ctx, &mcp.CallToolParams{Name: "sample"}) if err != nil { log.Fatal(err) } fmt.Println(res.Content[0].(*mcp.TextContent).Text) // Output: would have created a message } // !-sampling // !+elicitation func Example_elicitation() { ctx := context.Background() ct, st := mcp.NewInMemoryTransports() // Create a server with a tool that requests elicitation via the multi // round-trip pattern (SEP-2322): server-to-client requests are no longer // sent as standalone JSON-RPC calls on protocol version >= 2026-07-28. s := mcp.NewServer(&mcp.Implementation{Name: "server", Version: "v0.0.1"}, nil) mcp.AddTool(s, &mcp.Tool{Name: "ask"}, func(_ context.Context, req *mcp.CallToolRequest, _ struct{}) (*mcp.CallToolResult, any, error) { if len(req.Params.InputResponses) == 0 { return &mcp.CallToolResult{ InputRequests: mcp.InputRequestMap{"input": &mcp.ElicitParams{ Message: "This should fail", RequestedSchema: &jsonschema.Schema{ Type: "object", Properties: map[string]*jsonschema.Schema{ "test": {Type: "string"}, }, }, }}, }, nil, nil } res := req.Params.InputResponses["input"].(*mcp.ElicitResult) fmt.Println(res.Content["test"]) return &mcp.CallToolResult{}, nil, nil }) ss, err := s.Connect(ctx, st, nil) if err != nil { log.Fatal(err) } defer ss.Close() c := mcp.NewClient(&mcp.Implementation{Name: "client", Version: "v0.0.1"}, &mcp.ClientOptions{ ElicitationHandler: func(context.Context, *mcp.ElicitRequest) (*mcp.ElicitResult, error) { return &mcp.ElicitResult{Action: "accept", Content: map[string]any{"test": "value"}}, nil }, }) clientSession, err := c.Connect(ctx, ct, nil) if err != nil { log.Fatal(err) } if _, err := clientSession.CallTool(ctx, &mcp.CallToolParams{Name: "ask"}); err != nil { log.Fatal(err) } // Output: value } // !-elicitation