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.

🚀 New: Per-Source Documentation Tools

Each documentation source you provide now gets its own dedicated fetch tool!

• Instead of a generic list_doc_sources or fetch_docs tool, the MCP server dynamically creates a separate tool for each documentation source (e.g., each llms.txt file or local doc path you configure).
• These tools are named after the source (e.g., fetch_docs_LangGraph, fetch_docs_LangChain, etc.) and are visible up front in your MCP client (Cursor, Windsurf, Claude, etc.).
• Benefit: You no longer have to guess or discover which documentation sources are available—every source is directly accessible as its own tool, making it much easier to fetch docs for a particular package or library.
• This also makes it easier to audit and control which documentation is being accessed by your LLM agent.

Example:

If you configure two sources:

• LangGraph: https://langchain-ai.github.io/langgraph/llms.txt
• LangChain: https://python.langchain.com/llms.txt

you will see two tools:

• fetch_docs_LangGraph
• fetch_docs_LangChain

Each tool fetches and returns the documentation content for its specific source, converting it to markdown and handling errors.

---

llms-txt

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

Library	llms.txt
LangGraph Python	https://langchain-ai.github.io/langgraph/llms.txt
LangGraph JS	https://langchain-ai.github.io/langgraphjs/llms.txt
LangChain Python	https://python.langchain.com/llms.txt
LangChain JS	https://js.langchain.com/llms.txt

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 sources using a JSON config file:

Create a config file (e.g., sample_config.json):

[
  {
    "name": "LangGraph",
    "llms_txt": "https://langchain-ai.github.io/langgraph/llms.txt"
  },
  { "name": "LangChain", "llms_txt": "https://python.langchain.com/llms.txt" }
]

Then run:

uvx --from mcpdoc mcpdoc \
    --json sample_config.json \
    --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",
        "--json",
        "sample_config.json",
        "--transport",
        "stdio"
      ]
    }
  }
}

• Confirm that the server is running in your Cursor Settings/MCP tab.
• Best practice is to then update Cursor Global (User) rules.
• Open Cursor Settings/Rules and update User Rules with the following (or similar):

for ANY question about LangGraph, use the langgraph-docs-mcp server to help answer --
- call the fetch_docs_LangGraph tool to get the available llms.txt file
- reflect on the urls in llms.txt
- reflect on the input question
- call fetch_docs_LangGraph or fetch_docs_LangChain on any urls relevant to the question

• CMD+L (on Mac) to open chat.
• Ensure agent is selected.

Then, try an example prompt, such as:

what are types of memory in LangGraph?

Connect to Windsurf

• Open Cascade with CMD+L (on Mac).
• Click Configure MCP to open the config file, ~/.codeium/windsurf/mcp_config.json.
• Update with langgraph-docs-mcp as noted above.

• Update Windsurf Rules/Global rules with the following (or similar):

for ANY question about LangGraph, use the langgraph-docs-mcp server to help answer --
- call the fetch_docs_LangGraph tool to get the available llms.txt file
- reflect on the urls in llms.txt
- reflect on the input question
- call fetch_docs_LangGraph or fetch_docs_LangChain on any urls relevant to the question

Then, try the example prompt:

• It will perform your tool calls.

Connect to Claude Desktop

• Open Settings/Developer to update ~/Library/Application\ Support/Claude/claude_desktop_config.json.
• Update with langgraph-docs-mcp as noted above.
• Restart Claude Desktop app.

Note

If you run into issues with Python version incompatibility when trying to add MCPDoc tools to Claude Desktop, you can explicitly specify the filepath to python executable in the uvx command.

Example configuration

{
  "mcpServers": {
    "langgraph-docs-mcp": {
      "command": "uvx",
      "args": [
        "--python",
        "/path/to/python",
        "--from",
        "mcpdoc",
        "mcpdoc",
        "--json",
        "sample_config.json"
      ]
    }
  }
}

Note

Currently (3/21/25) it appears that Claude Desktop does not support rules for global rules, so append the following to your prompt.

<rules>
for ANY question about LangGraph, use the langgraph-docs-mcp server to help answer --
- call the fetch_docs_LangGraph tool to get the available llms.txt file
- reflect on the urls in llms.txt
- reflect on the input question
- call fetch_docs_LangGraph or fetch_docs_LangChain on any urls relevant to the question
</rules>

• You will see your tools visible in the bottom right of your chat input.

Then, try the example prompt:

• It will ask to approve tool calls as it processes your request.

Connect to Claude Code

• In a terminal after installing Claude Code, run this command to add the MCP server to your project:

claude mcp add-json langgraph-docs '{"type":"stdio","command":"uvx" ,"args":["--from", "mcpdoc", "mcpdoc", "--json", "sample_config.json"]}' -s local

• You will see ~/.claude.json updated.
• Test by launching Claude Code and running to view your tools:

$ Claude
$ /mcp

Note

Currently (3/21/25) it appears that Claude Code does not support rules for global rules, so append the following to your prompt.

<rules>
for ANY question about LangGraph, use the langgraph-docs-mcp server to help answer --
- call the fetch_docs_LangGraph tool to get the available llms.txt file
- reflect on the urls in llms.txt
- reflect on the input question
- call fetch_docs_LangGraph or fetch_docs_LangChain on any urls relevant to the question
</rules>

Then, try the example prompt:

• It will ask to approve tool calls.

Command-line Interface

The mcpdoc