@alsania-io/mcp-code-mode

Code-mode MCP server. Connects to child MCP servers, exposes their tools as TypeScript definitions, and executes LLM-authored code against them in a sandboxed node:vm context.

Collapses N tool-call round-trips into a single code execution. Inspired by CodeAct (Apple, ICML 2024), Cloudflare Code Mode, and mcpcodeserver.

Meta-tools exposed

| Tool | Purpose | |---|---| | list_servers | Enumerate configured child servers and their tool counts. | | get_tool_definitions | Return TypeScript interfaces for child tools (optionally filtered by server_names). Call this before writing code. | | generate_and_execute_code | Run LLM-authored TypeScript in a sandbox with all discovered tool functions available. |

Install

npm install @alsania-io/mcp-code-mode

Or run directly via npx:

npx @alsania-io/mcp-code-mode --config ./config.json

Config

Point --config at a JSON file describing child servers. See example-config.json.

{
  "version": 1,
  "servers": [
    { "name": "registry", "command": "node", "args": [".../mcp-server.mjs"] },
    { "name": "context7", "command": "npx", "args": ["-y", "@upstash/context7-mcp"] }
  ],
  "sandbox": { "timeoutMs": 30000, "maxOutputBytes": 200000 },
  "security": { "allowAllHosts": false, "allowedHosts": [] }
}

Env values support ${VAR} expansion from process.env at load time. Never commit real keys — use ${VAR} placeholders.

Lazy child spawning

Children are not spawned at startup. They are constructed at boot and connected on first use (list_servers, get_tool_definitions, or generate_and_execute_code). An idle code-mode process holds zero child processes. Connections are memoized and race-safe; a failed connect is recorded and does not block other children.

Development

make install     # install deps
make typecheck   # tsc --noEmit
make test        # vitest
make build       # emit dist/

License

MIT © Alsania

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