sigil-mcp

Library for building Model Context Protocol clients and servers in Sigil. Provides the server loop, JSON-RPC 2.0 framing, and channel-based message routing primitives so any Sigil project can expose tools and resources to MCP clients.

sigil-cli ships a built-in dev-tools server on top of this library, invoked via sigil mcp serve, which exposes documentation, lint, format, test execution, and nREPL-backed evaluation so AI agents can work idiomatically against a live Sigil project.

Modules

Module	Purpose
`(sigil mcp)`	Top-level re-exports plus package-tool discovery
`(sigil mcp server)`	Server loop, message routing, handler registration
`(sigil mcp client)`	Client lifecycle, correlation, cancellation, events
`(sigil mcp protocol)`	JSON-RPC 2.0 framing and MCP message shapes
`(sigil mcp channel)`	Helpers for channel-based server transports

Building your own MCP server

(import (sigil mcp))

(define server
  (mcp-server name: "my-server" version: "1.0"))

(mcp-server-register-tool! server
  name: "echo"
  description: "Echoes its input back."
  handler: (lambda (args) ...))

(mcp-server-run server)

For a complete example, see sigil-cli's (sigil cli mcp) module or projects like bureau, courier, folio, and minder.

Build and test

sigil deps install
sigil build
sigil test --report

The sigil executable bundles the released MCP modules. When testing local changes to a module that is also built in, add -L src before the command so the checkout takes precedence:

sigil -L src test test/test-protocol.sgl test/test-client.sgl --report

Run unchanged server integration suites through the normal package test path; the current toolchain's source-path override does not expose every private server binding used by those tests:

sigil test test/test-server.sgl test/test-nrepl-tools.sgl test/test-channel.sgl --report

Local development against an unreleased sigil monorepo:

sigil deps install --redirects ./dev-redirects.sgl
sigil build --redirects ./dev-redirects.sgl

License

BSD-3-Clause. See LICENSE in the sigil monorepo for the canonical copy.