MCP Server

A Dart plugin for implementing Model Context Protocol (MCP) servers. This plugin allows Flutter applications to expose data, functionality, and interaction patterns to Large Language Model (LLM) applications in a standardized way.

Features

• Every MCP revision, 2024-11-05 through 2026-07-28, plus the 2026-07-28 tasks extension — see Protocol Versions below
• Core primitives — Resources, Tools, Prompts, plus Completions (2025-06-18+)
• Server-initiated requests — requestClientSampling, requestClientRoots, requestClientElicitation with response routing and timeout
• Authorization — every HTTP request is decided before dispatch (401 / 403 with WWW-Authenticate), Protected Resource Metadata (RFC 9728), audience and scope checks
• Structured tool output (2025-06-18) — outputSchema + structuredContent + resource_link content type
• Icons + sampling tool calls (2025-11-25) — Tool.icons / Resource.icons / Prompt.icons, plus the new tools / toolChoice fields on sampling/createMessage
• List-changed notifications — spec-canonical notifications/{tools,resources,prompts}/list_changed
• Progress + cancellation — outbound notifyProgress; inbound notifications/cancelled and notifications/progress listeners
• Session events — onConnect / onDisconnect streams, per-session protocol version + capabilities
• Caching hints (2026-07-28) — ttlMs / cacheScope on discover, lists and reads (cacheTtl, publicLists)
• Health + metrics — getHealth(), named timers, custom counters
• Transports — stdio, SSE (legacy), Streamable HTTP (canonical 2025-03-26+)
• Platforms: wherever dart:io is available (Android, iOS, Linux, Windows, macOS)

Protocol Versions

Implements every revision of the Model Context Protocol; each client gets the one it opens with.

initialize negotiates among McpProtocol.supportedVersions (2025-11-25 and earlier). 2026-07-28 has no handshake: on stdio a request naming its version in _meta is served in that revision; over Streamable HTTP it is served on the same endpoint as the session revisions. A server that keeps per-session state sets enableStateless: false (TransportConfig.streamableHttp or StreamableHttpServerConfig), and 2026-07-28 clients fall back to initialize.

Coming from 2.x: MIGRATION-3.0.md.

Tasks