Keystone

What it does

Keystone is a framework for "charter engineering," allowing developers to author a structured set of standards (a charter) at the repository level to constrain and guide the behavior of AI coding agents. It ensures that any agent operating on a project—whether it is Claude Code, Cursor, or Codex—follows a consistent set of rules, roles, and workflows defined in plain markdown files.

Tools

• keystone_list_primitives: Lists all charter elements (guides, sensors, agents, etc.).
• keystone_get_primitive: Retrieves the content of a specific charter primitive.
• keystone_get_corpus: Fetches the detailed reasoning behind a specific rule.
• keystone_search: Performs full-text search across the entire charter.
• keystone_eval_run: Executes static and sensor evaluations to check project health.
• keystone_new_<kind>: Programmatically creates new charter primitives.

Installation

Install via Homebrew and initialize your project:

brew install tacoda/tap/keystone
keystone init
keystone mcp install --agent claude-code

Claude Desktop Config:

{
  "mcpServers": {
    "keystone": {
      "command": "keystone",
      "args": ["mcp", "serve"]
    }
  }
}

Supported hosts

Claude Code, Cursor, Codex, opencode