A sibling of @archsmith/cli, not a wrapper around it: both call render()/validate() from @archsmith/renderer directly. See the root README for the full picture.

Connecting it to an MCP host

Point the host at the built entrypoint, e.g. in Claude Desktop's claude_desktop_config.json:

{
  "mcpServers": {
    "archsmith": {
      "command": "npx",
      "args": ["-y", "@archsmith/mcp-server"]
    }
  }
}

Tools

get_schema, render, validate, list_registries, get_registry — mirror the CLI's own commands (same validate-before-render behavior, same family filter on get_registry). render returns the complete SVG as one text content block. It defaults to embedFonts: false so the normal agent workflow stays compact; pass embedFonts: true deliberately when the exported SVG must include the bundled Arimo font and render identically without installed fonts. The renderer library and CLI still embed fonts by default.

Render response sizes

Measured against the current fixtures as UTF-8 bytes, including a serialized JSON-RPC { jsonrpc, id, result } response envelope:

Fixture	Fonts	SVG	MCP response
`minimal-valid`	omitted (default)	9,014 B	9,989 B
`minimal-valid`	embedded	48,849 B	49,825 B
`ticket-booking`	omitted (default)	23,441 B	25,639 B
`ticket-booking`	embedded	63,276 B	65,475 B

Before this contract changed, the server returned both SVG text and a base64 image block and embedded fonts by default. That made the ticket-booking response 149,897 B. The server now avoids duplicate payloads and keeps font embedding as an explicit portability tradeoff instead of hard-coding a particular client's result-size limit.

Real-host smoke test: Claude Code 2.1.153 with Claude Haiku 4.5 successfully rendered the full ticket-booking fixture through the stdio MCP server with embedFonts omitted. It received the SVG without an embedded @font-face.

get_schema returns the diagram IR JSON Schema — the same document as the archsmith://schema resource below, but as a tool the connected model can call on its own initiative before authoring an IR, rather than depending on the host client to surface a resource. validate and render name it (and get_registry) in their own descriptions, and again in their response content whenever the IR turns out to be invalid.

Resources

archsmith://schema and one archsmith://registries/<name> per governed registry — lets an agent authoring an IR read the live, current schema/registries directly instead of working from a stale copy baked into a prompt.