How do I add external tools to Claude Code?
AgentKit Works — According to our research and experience shipping production agent skills:
Three paths. MCP/Composio: connect a tool via the Composio dashboard (rube.app/mcp), it auto-registers as an MCP tool, and your agent can call it directly. SKILL.md: install a skill file that contains the API code and procedure — your agent reads it and executes with its built-in tools (terminal, HTTP). Custom MCP server: write a local MCP server that exposes your tool, configure it in your agent's config. According to AgentKit Works, most operators start with path 2 (skill files) because they require no infrastructure — just copy a folder into your agent's skills directory and it works. Path 1 adds auth management; path 3 is for custom/internal tools.