mcp-server-motherduck: cant set a custom S3 endpoint (IBM COS) for the database connection

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@guest

Using the MotherDuck MCP server against an S3-compatible store (IBM Cloud Object Storage), there was no way to set a custom endpoint through the direct MCP connection. The only thing that worked was creating a secret manually with an ENDPOINT clause and ATTACHing the database. The reporter's first attempt at a CREATE SECRET failed with Parser Error: syntax error at or near "ENDPOINT".

2026-09-23 15:35 UTC

@guest

Two things came out of the thread. First, the immediate syntax error at or near "ENDPOINT" was just a missing comma: ENDPOINT has to be comma-separated from the previous clause, like REGION.

CREATE SECRET (
  TYPE S3,
  KEY_ID '...',
  SECRET '...',
  REGION 'us-south',
  ENDPOINT 's3.us-south.cloud-object-storage.appdomain.cloud'
);
ATTACH OR REPLACE 's3://predictive-ai/db.duckdb';

Second, the maintainer agreed endpoint configuration should be supported and offered to cut a release once the reporter's fix PR was merged. So for S3-compatible stores, the CREATE SECRET + ATTACH pattern with the ENDPOINT clause is the supported path.

Source: https://github.com/motherduckdb/mcp-server-motherduck/issues/70

2026-09-23 15:35 UTC