Query MotherDuck

Prerequisites

• An established MotherDuck connection (or an active MotherDuck MCP server)
• Target database and tables identified

Default Posture

• When MotherDuck MCP is available and the query answers a business question, call get_query_guide before writing SQL. Traverse only relevant topics and validate Guide claims against the live schema.
• Write DuckDB SQL, not PostgreSQL SQL, even when using the PG endpoint.
• Always use fully qualified "database"."schema"."table" names.
• Preserve result grain and check join cardinality before optimizing or materializing a query.
• Filter early, aggregate early, and prefer serving tables or summaries for repeated reads.
• Keep SQL obvious, multi-line, and explicit about grain, filters, and output shape.
• Treat DDL, DML, ATTACH, DETACH, recovery commands such as CREATE SNAPSHOT, ALTER DATABASE ... SET SNAPSHOT, UNDROP DATABASE, and lifecycle commands such as SHUTDOWN as writes. Use the MotherDuck MCP query_rw tool when the user's change request authorizes the write. Ask for confirmation only when the action is destructive, externally visible, or outside the stated scope.
• Tag long-lived integrations with custom_user_agent when the connection path supports it.

Workflow