cnpj

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

With no annotations provided, the description carries the full burden. It discloses that the input can be with or without punctuation and lists the output fields, which is useful. However, it does not mention error behavior (e.g., invalid CNPJ, not found) or any rate limits/auth requirements, which could be relevant for an API-based lookup. For a read-only lookup, this is adequate but not comprehensive.

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 sentences long, front-loads the purpose, and includes only high-value details (input flexibility and returned fields). Every word earns its place with no redundancy.

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 simple one-parameter lookup tool without an output schema, the description covers the essential aspects: what it does, how to format the input, and what data is returned. It does not detail edge cases or exhaustive output, but given the low complexity, it is sufficiently complete for an agent to call it 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?

The schema provides only the type 'string' with no description (0% coverage). The description compensates by explaining that the CNPJ can be provided with or without punctuation, which is a crucial formatting detail. It does not fully describe validation rules or length, but it adds significant meaning beyond the bare 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?

The description states a specific verb ('look up'), a resource ('Brazilian company'), and an identifier ('CNPJ'), which clearly distinguishes it from sibling tools like cep (postal code) or banks. It also lists the returned fields, leaving no ambiguity about what the tool does.

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 clearly identifies the use case (company lookup by CNPJ) and implicitly differentiates it from other lookup tools (CEP, banks, DDD, etc.). It does not explicitly mention when not to use it, but the resource and identifier make the context unambiguous, placing it above 'implied usage' yet below explicit exclusion guidance.

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