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Give your coding agent llms.txt as its starting point for FastMCP. This index links to the documentation as Markdown. Ask the agent to check your project’s installed version and read the relevant pages before writing code.

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Read version-matched documentation

For FastMCP 3, use the index entries under /v3/; unversioned pages describe FastMCP 4. Every page is available as Markdown by appending .md to its URL, such as the tools guide. Read the pages relevant to the task; llms-full.txt contains the entire documentation and may exceed your agent’s context window. Agents with MCP support can also search the documentation at https://gofastmcp.com/mcp. See LLM-friendly docs for a client example.

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Add authoring guidance

The optional fastmcp-server skill adds a workflow for building, extending, and reviewing servers: choose suitable MCP interfaces, preserve useful schemas and errors, consult version-matched documentation, and verify behavior through a real client. The documentation index helps the agent find API information; installing the skill makes this authoring guidance available for the agent to select across tasks. Install it with the Skills CLI, which lets you choose your coding agent:
The site’s skill discovery index lists the available skills. The skill source lives alongside FastMCP’s client CLI skill; the site publishes those same files. You can also install from the repository with npx skills add PrefectHQ/fastmcp --skill fastmcp-server. The skill uses the agent’s documentation access and code execution tools. Start a new agent session after installing. Ask it to use the fastmcp-server skill when working on your server. For example:
The skill is maintained in the FastMCP repository and evolves separately from package releases. Update your installed copy to pick up changes, or install from a Git revision when you need reproducible instructions. Your project’s dependency constraints still determine which FastMCP APIs the agent should use.
For an agent that needs to discover and call an existing server, use the client CLI skill. The server authoring skill is for writing server code.

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Verify the generated server

Run the server’s tests and inspect the schemas and results that clients receive. A successful import or the agent’s final message does not establish that the server works. The testing guide shows how to connect fastmcp.Client directly to your server without starting a network listener. For deployment work, also test the intended transport and authentication. Use local fixtures or a test account for operations that change data. If your server’s users need guidance for workflows spanning several operations, consider supplying skills with the server. The Skills Provider serves skill files as resources; the Experimental Skills Extension adds standard skills discovery. Check the installed FastMCP version and target host’s support, and verify that the host actually reads and uses the skill. Discovery alone does not activate it.