Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: it discloses the exact refusal categories, the verbatim permission error text to relay to users, caller-scoped visibility, and max_rows truncation. That is genuinely actionable behavior an agent could not infer from structured fields alone.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two dense sentences with the core action and row cap front-loaded, followed by preconditions and refusal semantics. Every clause carries information; nothing is restated from the annotations or schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists so return shape need not be explained, and the description still notes truncation reporting and error surfacing. For a read-only, caller-scoped query tool with four fully documented parameters, nothing an agent needs to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents sql, roles, principal and max_rows thoroughly, which sets the baseline at 3. The description reinforces the caller-scoping requirement ('for the same caller', 'the caller may not read') but adds no new syntax or format detail beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a precise verb and resource ('Execute one read-only SELECT and return the rows'), plus the output cap. It also implicitly separates itself from select_schema by framing the DDL from select_schema as input rather than something this tool produces, so an agent can tell the two apart immediately.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a clear precondition and workflow ('Write the SQL against the DDL select_schema returned for the same caller') and states what the tool refuses (writes, multiple statements, unreadable objects). It does not explicitly contrast with the 'answer' sibling, so a small routing gap remains.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.