503: service_unavailable error on tool call

[edwarddamato]

I'm using the MCP inspector to connect to Notion's MCP server at https://mcp.notion.com/mcp using Streamable HTTP.

The connection is established and I can correctly list the tools. However, when I make a tool call like the below, I get a 503: service_unavailable error.

Tool call:

{
  "method": "tools/call",
  "params": {
    "name": "fetch",
    "arguments": {
      "id": "25e378bc12c6807a9e37e1065292a325"
    },
    "_meta": {
      "progressToken": 1
    }
  }
}

Error:

{
  "name": "APIResponseError",
  "code": "service_unavailable",
  "status": 503,
  "headers": {},
  "body": "{\"object\":\"error\",\"status\":503,\"code\":\"service_unavailable\",\"message\":\"Public API service is temporarily unavailable, please try again later.\",\"request_id\":\"c2eb4b8e-9c0d-46cd-aab3-ac941be49bfd\"}"
}

I'm a little bit confused with this error and what's causing it. Anyone got any more information?