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

Annotations already declare read-only, idempotent, and non-destructive behavior; the description adds substantial non-obvious traits: the .txt download link is valid for one hour, the operation counts toward a 5-per-month quota, and the output is a formatted letter rather than a raw list. No contradiction with annotations.

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 efficiently structured sentences front-load the core purpose and output components, then pack the link validity, quota, and sibling alternative into a compact second sentence. No filler or repetition of schema fields.

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?

Despite having no output schema, the description explains what the returned artifact is (a .txt download link), its validity, quota impact, and content. Together with the fully documented input schema and safety annotations, this gives an agent enough to select and invoke the tool correctly.

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 baseline of 3 applies; the schema already explains client, date range, currency, greeting, and sign_off. The description does not materially deepen parameter meaning beyond noting the output includes a sign-off, so no higher score is warranted.

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?

The description opens with a specific verb+resource: 'Turn one client's statement into a plain-text letter for an email' and enumerates the delivered contents, including movements in date order, balances, deposit held, and a sign-off. It also explicitly contrasts with statement_pdf, making sibling differentiation immediate.

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?

It identifies a clear use context (email letter for one client) and names statement_pdf as the A4-page alternative. It does not explicitly rule out other sibling tools such as dunning_text or statements_report, but the plain-text/email framing gives sufficient direction.

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