Writing an MCP Server Package

An MCP server package registers an external tool server that the daemon connects to at runtime. This is the most common package type — wrapping an existing MCP server for one-command installation.

Minimal manifest

[package]
name = "my-server"
description = "What the server does"
keywords = ["relevant", "tags"]

[mcps.my-server]
command = "npx"
args = ["-y", "@scope/my-mcp-server"]

That’s it. On crabtalk hub install, this config is merged into the user’s config.toml and the server starts automatically.

Choosing a transport

MCP servers connect via stdio or HTTP. Use one or the other.

Stdio (most common) — the daemon spawns the process directly:

[mcps.my-server]
command = "npx"
args = ["-y", "@scope/my-mcp-server"]

HTTP — the server runs independently and the daemon connects to it:

[mcps.my-server]
url = "http://localhost:3000/mcp"

Environment variables

If the server needs API keys or configuration, declare them with empty defaults. The user fills them in after install:

[mcps.notion]
command = "npx"
args = ["-y", "@notionhq/notion-mcp-server"]
env = { NOTION_TOKEN = "" }

Post-install setup

If the server needs a setup step (e.g., downloading browser binaries), add [package.setup]:

[package.setup]
script = "npx playwright install chromium"

See the Playwright example for a complete manifest.