Cursor Spec (Plugin Marketplace, Rules, Commands, Skills, MCP)

Last verified: 2026-02-12

Primary sources

https://docs.cursor.com/context/rules
https://docs.cursor.com/context/rules-for-ai
https://docs.cursor.com/customize/model-context-protocol

Plugin Marketplace

Compound Engineering is published through the Cursor Plugin Marketplace.

In Cursor Agent chat, install with:

/add-plugin compound-engineering

Users can also search for "compound engineering" in the plugin marketplace.

The repo-owned marketplace files are:

.cursor-plugin/marketplace.json
plugins/compound-engineering/.cursor-plugin/plugin.json

Do not use the old custom Bun converter/install path for Cursor.

Config locations

Rules (.mdc files)

• Rules are Markdown files with the .mdc extension stored in .cursor/rules/.
• Each rule has YAML frontmatter with three fields: description, globs, alwaysApply.
• Rules have four activation types based on frontmatter configuration:

• Precedence: Team Rules > Project Rules > User Rules > Legacy .cursorrules > AGENTS.md.

Commands (slash commands)

• Custom commands are Markdown files stored in .cursor/commands/.
• Commands are plain markdown with no YAML frontmatter support.
• The filename (without .md) becomes the command name.
• Commands are invoked by typing / in the chat UI.
• Commands support parameterized arguments via $1, $2, etc.

Skills (Agent Skills)

• Skills follow the open SKILL.md standard, identical to Claude Code and Codex.
• A skill is a folder containing SKILL.md plus optional scripts/, references/, and assets/.
• SKILL.md uses YAML frontmatter with required name and description fields.
• Skills can be repo-scoped in .cursor/skills/ or user-scoped in ~/.cursor/skills/.
• At startup, only each skill's name/description is loaded; full content is injected on invocation.

MCP (Model Context Protocol)

• MCP configuration lives in .cursor/mcp.json (project) or ~/.cursor/mcp.json (global).
• Each server is configured under the mcpServers key.
• STDIO servers support command (required), args, and env.
• Remote servers support url (required) and optional headers.
• Cursor infers transport type from whether command or url is present.

Example:

{
  "mcpServers": {
    "server-name": {
      "command": "npx",
      "args": ["-y", "package-name"],
      "env": { "KEY": "value" }
    }
  }
}

CLI (cursor-agent)

• Cursor CLI launched August 2025 as cursor-agent.
• Supports interactive mode, headless mode (-p), and cloud agents.
• Reads .cursor/rules/, .cursorrules, and AGENTS.md for instructions.
• CLI permissions controlled via .cursor/cli.json with allow/deny lists.
• Permission tokens: Shell(command), Read(path), Write(path), Delete(path), Grep(path), LS(path).