MCP Client

A Dart plugin for implementing Model Context Protocol (MCP) clients. This plugin allows Flutter applications to connect with MCP servers and access data, functionality, and interaction patterns from 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. connect picks the revision with the server (ProtocolEra.auto)
• Unified transport configuration — sealed TransportConfig for stdio / SSE / Streamable HTTP
• OAuth 2.1 — the specification’s authorization flow (McpOAuth): discovery, registration, PKCE, resource, iss checks, step-up
• Result-typed error handling — Result from createAndConnect, plus McpError for spec error codes
• Core MCP primitives:
  • Resources — server data, URI templates, subscriptions
  • Tools — server-side functions, progress tracking, structured output (2025-06-18+)
  • Prompts — reusable interaction templates with completion (2025-06-18+)
  • Completion — complete(ref, argument) for completion/complete argument suggestions
  • Roots — filesystem boundary configuration; the server requests them via roots/list
  • Sampling — register a host LLM completion handler so the server can drive sampling/createMessage
  • Elicitation (2025-06-18) — register a user-input handler so the server can collect structured input (form and URL modes)
  • Tasks (2025-11-25) — callToolAsTask, getTask, taskResult, cancelTask
• Advanced:
  • Deferred Tool Loading — lightweight metadata + on-demand schema fetch (60–80% token reduction)
  • Progress notifications — outbound notifications/progress and inbound listener
  • Cancellation — notifyCancelled(requestId, reason) per spec notification
  • Resource subscriptions — notifications/resources/updated
  • Session management — automatic session validation and reconnection support
  • Ping — ping() probes the peer, and an inbound ping is answered automatically
• Cross-platform: Android, iOS, web, Linux, Windows, macOS (on the web, Streamable HTTP; stdio and HTTP+SSE need dart:io)

Protocol Versions

Implements every revision of the Model Context Protocol; the one in use is agreed with each server.