LLMS-TXT Documentation Server MCP Server

MCP LLMS-TXT Documentation Server

Overview

llms.txt is a website index for LLMs, providing background information, guidance, and links to detailed markdown files. IDEs like Cursor and Windsurf or apps like Claude Code/Desktop can use llms.txt to retrieve context for tasks. However, these apps use different built-in tools to read and process files like llms.txt. The retrieval process can be opaque, and there is not always a way to audit the tool calls or the context returned.

MCP offers a way for developers to have full control over tools used by these applications. Here, we create an open source MCP server to provide MCP host applications (e.g., Cursor, Windsurf, Claude Code/Desktop) with (1) a user-defined list of llms.txt files and (2) a simple fetch_docs tool read URLs within any of the provided llms.txt files. This allows the user to audit each tool call as well as the context returned.

llms-txt

You can find llms.txt files for langgraph and langchain here:

Quickstart

Install uv

• Please see official uv docs for other ways to install uv.

curl -LsSf https://astral.sh/uv/install.sh | sh

Choose an `llms.txt` file to use.

• For example, here's the LangGraph llms.txt file.

Note: Security and Domain Access Control

For security reasons, mcpdoc implements strict domain access controls:

1. Remote llms.txt files: When you specify a remote llms.txt URL (e.g., https://langchain-ai.github.io/langgraph/llms.txt), mcpdoc automatically adds only that specific domain (langchain-ai.github.io) to the allowed domains list. This means the tool can only fetch documentation from URLs on that domain.

2. Local llms.txt files: When using a local file, NO domains are automatically added to the allowed list. You MUST explicitly specify which domains to allow using the --allowed-domains parameter.

3. Adding additional domains: To allow fetching from domains beyond those automatically included:

   • Use --allowed-domains domain1.com domain2.com to add specific domains
   • Use --allowed-domains '*' to allow all domains (use with caution)

This security measure prevents unauthorized access to domains not explicitly approved by the user, ensuring that documentation can only be retrieved from trusted sources.

(Optional) Test the MCP server locally with your `llms.txt` file(s) of choice:

uvx --from mcpdoc mcpdoc \
    --urls "LangGraph:https://langchain-ai.github.io/langgraph/llms.txt" "LangChain:https://python.langchain.com/llms.txt" \
    --transport sse \
    --port 8082 \
    --host localhost

• This should run at: http://localhost:8082

• Run MCP inspector and connect to the running server:

npx @modelcontextprotocol/inspector

• Here, you can test the tool calls.

Connect to Cursor

• Open Cursor Settings and MCP tab.
• This will open the ~/.cursor/mcp.json file.

• Paste the following into the file (we use the langgraph-docs-mcp name and link to the LangGraph llms.txt).

{
  "mcpServers": {
    "langgraph-docs-mcp": {
      "command": "uvx",
      "args": [
        "--from",
        "mcpdoc",
        "mcpdoc",
        "--urls",
        "LangGraph:https://langchain-ai.github.io/langgraph/llms.txt LangChain:https://python.langchain.com/llms.txt",
        "--transport",
        "stdio"
      ]
    }
  }
}

• Confirm that the server is running i