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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely new operational context — that calls do not consume the daily free limit and that the origin's protection limit still applies — which is exactly the quota/throttling information annotations cannot express. It stops short of describing output shape or latency, so a 4 rather than 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?

Three tight sentences: return contents first, then scope/behavioral caveats, then alternative routing. Every sentence carries information and the most decision-relevant content is front-loaded.

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?

There is no output schema, and the description compensates by naming the returned fields. Combined with annotations covering the safety profile and a fully documented single parameter, an agent has everything needed 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% and the single cnpj parameter is already documented as accepting input 'with or without punctuation.' The description adds only the phrase 'by CNPJ,' which duplicates the schema rather than extending it, so the baseline 3 applies.

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 the specific resource (a Brazilian company's registration record, keyed by CNPJ) and enumerates the returned fields (name, status, activity, address). It also explicitly contrasts itself with the sibling consulta_cnpj, so an agent can distinguish 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 when-not rule with the alternative named: 'For sanctions, tax status and a live CNIA check, use consulta_cnpj.' It further clarifies scope limits ('does not show contacts or partners and runs no extra checks'), leaving nothing to inference.

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