Architecture

This chapter tells how a request moves through RuleMCP.

Workspace

The repository is a private pnpm workspace with the name rule-mcp-workspace. It has three packages:

The root also holds bin/, skills/, personas/, prompts/, and scripts/. The server needs all of them at run time. All workspace packages are in the repository, so a clone builds with no other project.

Request path

An agent request follows these steps.

1. Agent

   The agent sends a prompt, a slash command, or a tool call.

2. Transport

   The default transport is stdio. A long-running local server uses HTTP and SSE.

3. Router

   rule_tool gives a score to the request and selects a skill or an area hub.

4. Skill or tool

   The skill serves its evidence: a styleguide, a template, or a pattern.

5. Guardrails

   Deterministic checks read the proposed code.

6. Response

   The agent receives structured content. The server does not call a model.

Surfaces

The surface map gives the live counts.

Skill layers

The server reads skills from three layers. The last layer that defines a name wins.

1. Native. The skills/ directory of the server.
2. Project. .rule-mcp/skills/ in the project.
3. User. skills/ in the runtime home, ~/.rule-mcp/skills/ by default.

Custom skills tells how to use these layers.

Design rules

• Local first. Skills are on disk. The core features need no network.
• Model-agnostic. There is no LLM inside the server.
• Registry-driven. The census and the agent commands read the same registries.
• Area hubs. A leaf skill has no slash command. An area hub reaches it.

Related pages

• Getting started
• Environment variables