The Docs by LangChain (streamable HTTP, url: https://docs.langchain.com/mcp) are enabled in Tools & MCP. The MCP logs show a successful connection and one tool found, but the available server is not listed when the Agent calls MCP; only user-lark-mcp and cursor-ide-browser are available.
Open a new Agent page and test the specific invocation of this MCP tool. The specific instructions are as follows: “用 Docs by LangChain 这个 MCP 里的 SearchDocsByLangChain 查一下 LangGraph 错误处理文档。”
Hey, this is a known issue. MCP servers can show as connected and you might see tools in the logs, but the agent still doesn’t pick them up in the session.
A few workarounds that have helped other users with the same problem:
Toggle the MCP server off and on in Cursor Settings > Tools & MCP. This forces a re-init. Sometimes toggling any MCP server triggers a refresh for all of them.
Start a fresh chat after toggling. Existing sessions might not pick up newly available tools.
Mention the MCP server by name in your first message. Instead of a generic prompt, try something like: “Using the Docs by LangChain MCP, search for LangGraph error handling docs.” This can nudge the agent to discover the tool.
There might be a timing delay between the server showing as connected in the UI and the agent actually having access to the tools. Waiting a moment after it connects, then starting a new chat, can help.
A couple questions:
What status does the LangChain Docs server show in Settings > Tools & MCP, green, yellow, or red?
Is this configured globally ~/.cursor/mcp.json or at the project level .cursor/mcp.json?
The team is aware of this pattern and tracking it. Your report helps with prioritization.