Run a single read-only SELECT (or WITH...SELECT / UNION) against a database.

connection is a named server from your config (defaults to the configured default_connection). schema sets the default database/namespace for the query (defaults to that connection's default_schema); table names can still be schema- qualified to read across schemas on the same connection. Call list_connections() if unsure what's available, list_schemas(connection) to see schemas on one.

Writes, DDL, multiple statements, INTO OUTFILE and dangerous functions are rejected. Output is capped; when truncated is true, pass the suggested offset to page.

EXPLAIN FORMAT=JSON for a SELECT — query plan (indexes, join order, estimated rows) without executing it. Same connection/schema routing as run_select.

List the connections you can query, with each one's default schema, any described schemas, whether it is gated (require_opt_in) and currently enabled.

Call this FIRST when unsure what to target. Query one with run_select(..., connection=, schema=). Gated connections show enabled=false until RODB_ENABLE_GATED opts them in.

List the schemas (databases) visible on a connection's server, with any descriptions you configured. System schemas are hidden. Use this to discover which schema to pass to the other tools.

List tables and views in the resolved schema (name, type, engine, approx rows).

Columns of a table: name, type, nullability, key, default, extra, comment.

Indexes of a table: name, columns (in order), uniqueness, type, cardinality.

Foreign keys on a table (outbound) and FKs pointing to it (inbound).

Approximate size of a table: row estimate, data/index bytes, engine, timestamps.