lookup_broker

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

No annotations are provided, so the description carries the behavioral disclosure burden. It correctly implies this is a read-only operation by describing it as a 'look up' returning registered data. However, it doesn't disclose potential edge cases like unknown CNPJs (does it throw or return empty?), data recency, or CVM data update cadence.

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 description is two tightly-written paragraphs: one sentence for the core action and one for the returned data fields. Every sentence earns its place with no fluff or repetition of schema information.

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 an output schema present, the description needn't enumerate the full return structure, but it helpfully names the key returned fields (trade name, legal name, status, address, contacts). For a simple one-parameter lookup tool with complete schema coverage, the combination of description, schema, and output schema provides adequate completeness.

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 sole parameter 'cnpj' already has a clear description including the punctuation-flexibility note (14 digits, with or without punctuation). The tool description reinforces the CNPJ is the lookup key but adds no new semantic detail beyond the schema, so baseline 3 is appropriate.

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 clearly states the verb ('look up') and resource ('CVM-authorized brokerage firm') and specifies the lookup key (CNPJ). The return payload is enumerated (trade name, legal name, status, address, contacts), distinguishing it from sibling tools like lookup_cnpj which is a general CNPJ lookup, not broker-specific.

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?

The description establishes clear context that this is for CVM-authorized (regulatory) brokerage firms in Brazil, which implies use when needing regulatory registration data. However, it does not explicitly state when to prefer this over the sibling lookup_cnpj or what limitations exist (e.g., only CVM-authorized firms), nor does it give exclusions.

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