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

The description explains why readOnlyHint=false matters (it consumes a paid lookup), discloses the 402 failure mode, the return path data.selo_sintonia with grade/cycle/validity or null, the legal reason other grades are hidden, and the no-double-charge rule for repeat checks in the same cycle. That is behavioral context well beyond what the annotations state.

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?

The purpose is front-loaded in the first sentence, followed by cost, error behavior, return shape, and caching in descending order of importance. Every sentence carries distinct information with no filler.

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?

With no output schema, the description still covers return structure, null semantics, error codes, and billing rules. An agent has everything needed to call this correctly and interpret the result.

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% and the single cnpj parameter is fully documented in the schema, including the alphanumeric format. The description adds nothing about the parameter itself, 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?

The first sentence states a specific verb and resource: checks at Receita Federal whether a company appears on the public Sintonia A+ seal list. This is narrow enough that an agent can distinguish it from generic siblings like consulta_cnpj or get_cnpj, though no alternative is named explicitly.

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 gives concrete operating context: one lookup from the paid package, no free quota, 402 with offers when balance is missing. It doesn't name a sibling to use instead for non-seal company data, so the when-not guidance is only implied.

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