A SKILL.md file teaches your AI coding assistant domain-specific knowledge about a service's API — the things that aren't captured in tool names or parameter descriptions.
Skills are an open standard supported by 27+ AI agents including Claude Code, Cursor, Codex, Gemini CLI, and VS Code.
A skill encodes what you'd learn after using an API for a week. It doesn't list tools — your AI already has list_tools for that.
Data model hierarchies, object relationships, and how a service organizes its concepts. The stuff you'd learn after using the API for a week.
Multi-step sequences like "create Customer before Subscription" or "look up pipeline stages before setting a deal stage." The ordering the AI wouldn't know.
Non-obvious behaviors, common mistakes, and API quirks — like "feature flag deletion is permanent" or "use $pathname instead of $current_url for breakdowns."
Skills use a lightweight discovery model. Your AI reads the name and description (~100 tokens) at startup and only loads the full skill when a matching task is detected.
Your AI already gets tool names, descriptions, and full parameter schemas from MCP. A skill that repeats this is wasted tokens.
Authentication, credential configuration, and API keys are handled by the MCP platform. Skills focus on how to use the API effectively, not how to connect.
MCPBundles skills are different from generic skills — they're written for the exact tools in each bundle and backed by real authenticated API access.
Teaches domain knowledge
Provides authenticated tool access
Together, your AI knows how and can interact with third-party services.
Save the SKILL.md file to the right location in your project and your agent picks it up automatically.
.claude/skills/{name}/SKILL.md.cursor/rules/{name}.md.agents/skills/{name}/SKILL.md.github/copilot-instructions.md.windsurfrules/{name}.md.agents/skills/{name}/SKILL.md