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

Goes well beyond the annotations by disclosing the quota economics: unlock consumes 1 monthly query, stays open until month-end, and re-opening is free; Pro accounts bypass the cost entirely. It also names the `points_left` response field and warns that readOnlyHint=false stems from account-state consumption, so the mutation profile is fully explained.

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?

Front-loads the core behavior (12-month window) before the cost details, and each sentence carries non-redundant information about quota, Pro bypass, or output fields. It is somewhat dense with parenthetical asides and could be tightened, but nothing is wasted.

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 quota-metered tool with no output schema, the description supplies everything an agent needs: cost model, idempotence of re-opening, Pro exemption, the `points_left` return field, and the display convention for `fipe_year_label`. Nothing material is left unstated.

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 67%, and the one undocumented parameter (`unlock`) is the most consequential — the description fully explains its cost, duration, and bypass conditions. It also adds a display rule tied to `year` (show '0 km' rather than 32000), though it doesn't restate the FIPE code format already in 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 specific verb+resource: monthly FIPE price for a given FIPE code and model year, scoped to the last 12 months. The 'last 12 months vs. full history since 2001' framing implicitly separates it from get_fipe_valuation, but no sibling is named explicitly, so an agent must infer the boundary.

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 when-to-use rule for the cost-bearing path: 'Use `unlock=true` only when the user asks for the complete history,' plus the Pro-account carve-out. It does not say when to prefer this tool over get_fipe_valuation or get_technical_specs, but the conditional guidance on unlock is precise.

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