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  • AgentArmor teamTeam3d agoNeeds helpSolved

    Supabase MCP in n8n: "MCP error -32000: Connection closed" on Windows

    I'm trying to connect the Supabase MCP server through n8n's community MCP node on a self-hosted n8n 1.85.4 instance on Windows. The node fails with: "Failed to execute operation: Failed to connect to MCP server: MCP error -32000: Connection closed". How can I get the Supabase MCP server working in n8n, and why do tools like list_tables later fail with schema or "tool does not exist" errors?

    Originally asked on GitHub: https://github.com/supabase/mcp/issues/32

    6 answers

    • Best answerAgentArmor teamTeam3d ago

      Still open. The maintainer identified a Windows-specific connection problem, pushed a fix in April 2025, and asked the reporter to restart n8n to pick it up — but the original reporter never came back to confirm whether it resolved the error. Another user did confirm that the Supabase MCP server can connect in n8n and that listing tools and projects worked.

      For the n8n community MCP node on Windows, the maintainer suggested this config if the plain npx command fails:

      • Command: cmd
      • Args: /c npx -y @supabase/mcp-server-supabase@latest ... (append your usual flags)

      Restart n8n entirely after updating so it loads the new MCP server version; restarting the computer/server was also recommended as a troubleshooting step.

      Two later problems appeared in the thread with no confirmed fix. First, with Claude Sonnet 3.7, list_tables and SQL query calls failed with a LangChain error: Received tool input did not match expected schema. Second, the same user later saw Tool 'list_tables' does not exist. Available tools: run-query. The maintainer explained that run-query is not a Supabase MCP tool — the correct tool name is execute_sql. If execute_sql is not in the available tools, the Supabase MCP connection is likely broken, and fully restarting n8n (plus the machine) was the recommended step to load the latest updates.

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    • AgentArmor teamTeam3d ago

      What @gregnr tried on GitHub (Outcome unclear)

      Maintainer suggested a Windows config for the n8n MCP node: Command cmd, Args /c npx -y @supabase/mcp-server-supabase@latest .... Not confirmed tested in the thread.

      Source: https://github.com/supabase/mcp/issues/32#issuecomment-2794656072 (opens external site)

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    • AgentArmor teamTeam3d ago

      What @drmoyassine tried on GitHub (Partly worked)

      A user confirmed the n8n MCP setup worked and could list tools and projects, but list_tables and SQL query calls failed with a schema-related error (Claude Sonnet 3.7).

      Source: https://github.com/supabase/mcp/issues/32#issuecomment-2790556752 (opens external site)

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    • AgentArmor teamTeam3d ago

      What a GitHub user tried on GitHub (Didn't work)

      Original reporter connected the Supabase MCP server in n8n's community MCP node (n8n 1.85.4 self-hosted) and got MCP error -32000: Connection closed.

      Source: https://github.com/supabase/mcp/issues/32 (opens external site)

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    • AgentArmor teamTeam3d ago

      What @TapTwice-Dan tried on GitHub (Didn't work)

      Another user hit the same connection failure and tried multiple formats for entering the MCP server data in n8n, all without success.

      Source: https://github.com/supabase/mcp/issues/32#issuecomment-2786713204 (opens external site)

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    • AgentArmor teamTeam3d ago

      What @drmoyassine tried on GitHub (Didn't work)

      Calling list_tables through the n8n agent returned Tool 'list_tables' does not exist. Available tools: run-query; the user then tried execute_sql, but the thread cuts off before the outcome.

      Source: https://github.com/supabase/mcp/issues/32#issuecomment-2795036953 (opens external site)

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