⚠️ Breaking Changes

The Result.Meta field type has changed from map[string]any to *Meta. Code that directly accesses or sets this field will need to be updated:

// Before (v0.36.0 and earlier):
result.Meta = map[string]any{"key": "value"}

// After (v0.37.0):
result.Meta = &mcp.Meta{AdditionalFields: map[string]any{"key": "value"}}

What's Changed

• Replace Prompts/Resources/Resource Templates by @dgageot in #518
• Update server.go race condition by @outofthisworld in #524
• task: add _meta field to relevant types as defined in MCP specification by @buraksenn in #429
• feat: implement sampling support for Streamable HTTP transport by @andig in #515
• Fix SSE transport not properly handling HTTP/2 NO_ERROR disconnections by @okoshi-f in #509
• feat: add thread-safe SetExpectedState for cross-request OAuth flows by @sd2k in #500
• feat: allow to set a custom logger in the SSE and STDIO clients by @caarlos0 in #525

New Contributors

• @outofthisworld made their first contribution in #524
• @buraksenn made their first contribution in #429
• @andig made their first contribution in #515
• @okoshi-f made their first contribution in #509
• @caarlos0 made their first contribution in #525

Full Changelog: v0.36.0...v0.37.0

What's Changed

• Add defs field to ToolsInputSchema by @ostafen in #488
• Remove sampling_server binary file by @JeffreyCA in #512
• chore: remove comments related to JSON-Batching by @cryo-zd in #514
• feat: support structured content and output schema by @pottekkat in #460
• Hide error log when it's not useful by @dgageot in #517

New Contributors

• @ostafen made their first contribution in #488
• @JeffreyCA made their first contribution in #512
• @dgageot made their first contribution in #517

Full Changelog: v0.35.0...v0.36.0

What's Changed

• Http headers by @adityamj in #480
• fix: check if resp is nil on error for initialize methods by @pottekkat in #492
• Fix race condition in stdio.SendRequest with canceled context by @ezynda3 in #503
• Embed client capabilities into the Session by @ardaguclu in #491
• enhc(server): allow adding multiple resource templates at once by @rafaeljusto in #483
• Get rid of binary file. by @wkoszek in #505
• feat: implement protocol version negotiation by @ezynda3 in #502

New Contributors

• @adityamj made their first contribution in #480
• @ardaguclu made their first contribution in #491
• @rafaeljusto made their first contribution in #483
• @wkoszek made their first contribution in #505

Full Changelog: v0.34.0...v0.35.0

What's Changed

• fix(streamable_http): ensure graceful shutdown to prevent close reque… by @sunerpy in #477
• fix(streamble_http) SendNotification not work bug by @Robin-ZMH in #473
• refactor: replace fmt.Errorf with TransportError wrapper by @AdamShannag in #486
• fix Content-Type: application/json; charset=utf-8 error by @oldweipro in #478
• feat: Inprocess sampling support by @ezynda3 in #487
• feat: support in tool result handling & update example by @CocaineCong in #467
• feat(logging): add support for send log message notifications and implemented the SessionWithLogging interface on streamableHttpSession by @sunerpy in #484

New Contributors

• @sunerpy made their first contribution in #477
• @Robin-ZMH made their first contribution in #473
• @AdamShannag made their first contribution in #486
• @oldweipro made their first contribution in #478
• @CocaineCong made their first contribution in #467

Full Changelog: v0.33.0...v0.34.0

What's Changed

• fix(server): Fix the logic of the WithStateLess function by @dcsunny in #387
• fix(srv/stream): correct handleGet status code to 200 by @cryo-zd in #379
• Add an example of an in process client by @edwardcqian in #371
• feat: add type-safe array items helper functions by @davidleitw in #396
• Issue 400 fix by @ozzyozbourne in #406
• fix(client/transport/stream): check for nil pointer by @dinistavares in #404
• feat: add ResourceLink type and parsing support by @chenmingyong0423 in #407
• Fix docs by @ezynda3 in #430
• feat: client-side streamable-http transport supports continuously listening by @leavez in #317
• feature: add support ResourceTemplates to mcptest package by @Slach in #449
• Add support for MCP host session management by @C0deKing in #466
• docs: Fix unused import in readme example by @Squiry in #469
• Support creating an Stdio client with options by @peteski22 in #457
• Implement sampling in Stdio by @ezynda3 in #461

New Contributors

• @dcsunny made their first contribution in #387
• @edwardcqian made their first contribution in #371
• @davidleitw made their first contribution in #396
• @ozzyozbourne made their first contribution in #406
• @dinistavares made their first contribution in #404
• @chenmingyong0423 made their first contribution in #407
• @Slach made their first contribution in #449
• @C0deKing made their first contribution in #466
• @Squiry made their first contribution in #469
• @peteski22 made their first contribution in #457

Full Changelog: v0.32.0...v0.33.0

What's Changed

• feat(mcp): add NewToolResultErrorf by @icholy in #357
• feat(mcptest): extend test server with prompt and resource support by @vasayxtx in #346
• [streamable-http] Add ability to override the http.Client by @tra4less in #359
• fixed logo issue in home page by @asaf-shitrit in #364
• feat(mcptest): Change Server.Start to accept a context.Context. by @octo in #339
• fix(test/stdio): address io:read/write on closed pipe error by @cryo-zd in #360
• [SSE][OAuth] Add OAuth support to SSE client by @giridhar-murthy-glean in #340
• More comprehensive docs by @ezynda3 in #374
• fix(srv/stream): properly remove sessionTool to prevent memory leak by @cryo-zd in #365
• fix: SSE parser now correctly handles events without event field by @ezynda3 in #376
• fix: ignore session IDs in stateless mode instead of rejecting them by @ezynda3 in #375
• support search www doc by @dugenkui03 in #378
• Optimize docs by @dugenkui03 in #386

New Contributors

• @icholy made their first contribution in #357
• @vasayxtx made their first contribution in #346
• @tra4less made their first contribution in #359
• @asaf-shitrit made their first contribution in #364
• @giridhar-murthy-glean made their first contribution in #340

Full Changelog: v0.31.0...v0.32.0

What's Changed

• [feat] separate request struct by @OswinWu in #333
• fix: logo on website is squashed by @corani in #349
• fix: panic when streamable HTTP server sends notification by @dugenkui03 in #348
• fix: move styles.css to www/docs by @corani in #354
• fix(server): resolve stdio server context cancellation bug by @sonirico in #331
• Add option to StreamableHTTPServer to allow custom http server instance by @yash025 in #347
• fix(Srv/stream): add ID field to PingRequest by @cryo-zd in #353

New Contributors

• @OswinWu made their first contribution in #333
• @corani made their first contribution in #349
• @sonirico made their first contribution in #331

Full Changelog: v0.30.1...v0.31.0

What's Changed

• fix(server): Implement MCP version negotiation. by @octo in #341

Full Changelog: v0.30.0...v0.30.1

What's Changed

• Feat: Impl Server-Side Streamable HTTP transport by @leavez in #273
• Support customize request header by @dugenkui03 in #315
• docs: add regeneration instructions by @pmenglund in #309
• docs(examples): correct use of GetArguments by @jamietanna in #316
• fix: avoid painc caused by writing to closed channel by @cryo-zd in #318
• docs: use helper functions and return error as result by @pottekkat in #322
• Update README.md by @dugenkui03 in #323
• Feat(prompts): add DeletePrompts method to MCPServer by @God-Jay in #320
• Scaffold documentation site by @ezynda3 in #324
• Docs by @ezynda3 in #325
• feat: Implement OAuth in the client by @ezynda3 in #296
• feat(server): persist client info in sessions by @ShawkyZ in #313

New Contributors

• @pmenglund made their first contribution in #309
• @jamietanna made their first contribution in #316
• @God-Jay made their first contribution in #320
• @ShawkyZ made their first contribution in #313

Full Changelog: v0.29.0...v0.30.0

What's Changed

• refactor: make CallToolRequest.Arguments more flexible (Breaking Change) by @ezynda3 in #287
• Drop unused fields from server.sseSession by @ggoodman in #303
• chore: remove unused variables and type arguments by @pottekkat in #302
• chore(Srv/stdio): duplicated setting of ErrorLogger by @cryo-zd in #306
• fix: handle the situation where the channel is closed by @button-chen in #304

Breaking Changes

In v0.29.0, MCP-Go introduces breaking changes to tool request handling. The main change is that request.Params.Arguments is no longer directly accessible as a map. Instead, you must use the new GetArguments() method to retrieve arguments as a map. For type-safe argument access, new helper methods like RequireString(), RequireFloat(), and RequireBool() have been added. To migrate:

1. Replace direct access to request.Params.Arguments["key"] with request.GetArguments()["key"]
2. For better type safety, use the new helper methods: request.RequireString("key"), request.RequireFloat("key"), etc.
3. For complex argument structures, use the new BindArguments() method with a struct, or try the new typed tool handlers with mcp.NewTypedToolHandler() as shown in the new examples/typed_tools example.

New Contributors

• @ggoodman made their first contribution in #303
• @button-chen made their first contribution in #304

Full Changelog: v0.28.0...v0.29.0