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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, yet the description still adds real value: it discloses that output is identical in shape to summarize_payouts minus Excel/PDF downloads, and it fences off capabilities an agent might otherwise assume (currency conversion, account linking, tax advice). The phrase 'does not need files' is potentially confusing next to a tool that accepts file and files inputs, which keeps this short of a 5.

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?

Single well-ordered paragraph: trigger with examples first, then the sibling alternative, then negative scope. Dense but every clause carries routing weight; the ambiguous 'does not need files' phrasing is the one sentence that doesn't land cleanly.

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?

For a read-only aggregation tool with a rich schema, full annotation coverage and an output schema, the description covers everything an agent needs: inputs accepted, output shape by reference to the sibling, and boundaries. No return-value documentation is required since the output schema exists.

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 coverage is 100% with self-documenting fields, so the baseline is 3. The description reinforces a few semantics (per-currency separation, the 1099-K/year framing, combined exports) but adds no new syntax or constraint detail beyond what the schema already spells out.

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 specific verb+resource (compute monthly sales totals from an export or pasted rows), enumerates the supported platforms, and names the exact sibling it is not (summarize_payouts for spreadsheet/PDF output). An agent can route between the two without opening either schema.

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 an explicit trigger ('when the user wants quick monthly sales totals ... and does not need files'), paraphrases real user utterances, names the alternative and the condition that selects it, and lists three exclusions (no account connection, no currency conversion, no tax advice).

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