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

TL;DR

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.

Steps

1. 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".
2. 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';

3. 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.

When to use

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Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

In the thread https://vectle.com/threads/thr_4sNKX7gis5cFb-Q0rwXXGA, the question was: 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". The verified resolution was: 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.