Resilient MCP Server

The Resilient compiler ships a built-in Model Context Protocol (MCP) server that exposes the full compilation pipeline as tools. AI assistants that speak MCP (Claude Desktop, Cursor, VS Code with the MCP extension, …) can use these tools to write, check, and run Resilient code without leaving their chat session.

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Quick start

# Activate the MCP server
rz mcp

The server reads one JSON-RPC message per line from stdin and writes one response per line to stdout (NDJSON — newline-delimited JSON, per the MCP 2024-11-05 spec). You typically don’t run it by hand; instead, register it in your MCP client’s config:

{
  "mcpServers": {
    "resilient": {
      "command": "rz",
      "args": ["mcp"]
    }
  }
}

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Tools

resilient_parse

Parse Resilient source and report syntax errors.

Input:

{ "source": "fn add(int a, int b) -> int { a + b }" }

Success output:

OK — parsed 1 top-level statement(s), no errors.

Error output:

Parse errors (1):
1:4: expected identifier

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resilient_typecheck

Parse + type-check source. Returns all type diagnostics.

Input:

{ "source": "fn f() -> int { \"hello\" }" }

Error output:

Type error:
1:17: return type mismatch: expected int, got string

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resilient_run

Execute Resilient source and capture stdout.

Input:

{ "source": "println(\"hello, world!\")" }

Success output:

Output:
hello, world!

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resilient_lint

Run all Resilient lint passes and return warnings.

Includes: naming conventions, dead code, unsafe call patterns, safety-critical violations, AI-threat detection, and more.

Input:

{ "source": "fn F(int x) -> int { x }" }

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resilient_format

Format / pretty-print Resilient source using the canonical formatter.

Input:

{ "source": "fn f(int x)->int{x+1}" }

Output:

fn f(int x) -> int {
  x + 1
}

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resilient_check

Full pipeline: parse + typecheck + all lint passes. Fastest way to validate a snippet end-to-end.

Input:

{ "source": "fn add(int a, int b) -> int { a + b }" }

Success output:

OK — parse, typecheck, and lint all passed.

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resilient_verify

Z3 SMT contract verification. Checks requires / ensures clauses on every function.

Note: Only available in builds compiled with --features z3. Without Z3, the tool returns a clear “not available” message.

Input:

{
  "source": "fn div(int x, int y) -> int\n  requires y != 0\n{ x / y }"
}

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Protocol notes

• Transport: stdio (NDJSON — one JSON object per line, flush after each)
• Protocol version: 2024-11-05
• No feature flags required: the MCP server is always available on native builds (it only depends on serde_json, which is already an unconditional dependency of the compiler).
• wasm32: not available (same constraint as the REPL and watch mode).

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Registry

The Resilient MCP server is published to the official MCP Registry under the namespace io.github.ericspencer00/resilient. The registration points at the multi-arch Docker image at ghcr.io/ericspencer00/resilient (both amd64 and arm64), so any MCP client that resolves servers from the registry can install Resilient with a single click without needing to clone or build from source.

server.json at the repo root is the source of truth for the registry entry; .github/workflows/mcp-publish.yml re-publishes it on every release: published event, syncing the version + OCI tag to the release.

Example session

→ {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}
← {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"tools":{}},"protocolVersion":"2024-11-05","serverInfo":{"name":"resilient","version":"0.2.0"}}}

→ {"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}
← {"jsonrpc":"2.0","id":2,"result":{"tools":[{"name":"resilient_parse",...},...]}}

→ {"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"resilient_run","arguments":{"source":"println(42)"}}}
← {"jsonrpc":"2.0","id":3,"result":{"content":[{"text":"Output:\n42\n","type":"text"}],"isError":false}}