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MCP (Model Context Protocol)

Juneau provides both server-side and client-side support for the Model Context Protocol (MCP), a JSON-RPC 2.0 protocol that lets AI assistants and agents discover and invoke external tools, prompts, and resources.

Two protocol revisions are supported side-by-side as separate, revision-bound Maven modules: 2025-06-18 and 2026-07-28 (the current revision). A client/server pair picks one revision at compile time — see Choosing your MCP setup for the full comparison, why the MCP ecosystem is 9 artifacts (3 shared cores + 6 per-revision adapters) rather than 6 independent ones, and why the two revisions are maintained differently going forward.

Where to start​

  • MCP Quickstart — a working server and client talking to each other in about 5 minutes.
  • Choosing your MCP setup — protocol revision, dedicated servlet vs mixin, plain vs Spring Boot.
  • MCP Recipes — copy-pasteable snippets for tools, prompts, resources, resource templates, completions, error handling, elicitation, and subscriptions.

Deep reference​

  • juneau-rest-server-mcp — full server-side API reference: capabilities, pagination, notifications, cache hints, tracing, Multi-Round-Trip Requests, elicitation, and subscriptions.
  • juneau-rest-client-mcp — full client-side API reference: the duplex server-request channel, auth, and response caching.
  • juneau-bean-mcp-v20250618 — the MCP wire-bean catalog underlying both the server and client modules.