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Question

Hi,

I’m using toolbox MCP to connect to BigQuery. When I try to read an external table connected to a Google Spreadsheet, I encounter the following error:

Error processing tool: [MCP][bigquery][execute_sql_tool] tool call failed: Error POSTing to endpoint (HTTP 500): {"jsonrpc":"2.0","id":203,"error":{"code":-32603,"message":"unable to execute query: googleapi: Error 403: Access Denied: BigQuery BigQuery: Permission denied while getting Drive credentials., accessDenied"}}

Here’s what I’ve already done:

Granted access to both the Google Drive API and the Google Sheets API.

Verified that the service account has the required permissions for the sheet.

However, the external table still cannot be read, and the query fails with the above error.

Is there any additional configuration or permission that I might be missing in order to allow BigQuery (through MCP toolbox) to access external tables backed by Google Sheets?

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