lookup_cep

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

No annotations are provided, so the description carries the full burden. It mentions local caching for 30 days, which is a useful behavioral detail. However, it does not disclose error handling, rate limits, or what happens if the CEP is invalid or offline. For a simple lookup, the caching detail is a positive addition.

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 short (two sentences) and front-loaded with the main purpose. Every word adds value: service provider, online dependency, return fields, and caching. No superfluous content.

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?

The output schema exists, so return values are covered. The description lists most relevant fields. However, it lacks input format details and error handling. For a simple tool, it is adequate but not thorough.

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 input schema has one parameter 'cep' with 0% description coverage. The description adds that it is a Brazilian CEP but does not explain expected format (e.g., with or without hyphen, digits only). No examples or validation rules are provided, leaving the agent to guess the required format.

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 tool consults Brazilian CEP via ViaCEP online, lists specific return fields (logradouro, bairro, cidade, UF, IBGE code, DDD), and mentions local caching. It effectively distinguishes itself from sibling tools like lookup_endereco_cep by specifying the exact service and output.

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?

No explicit when-to-use or when-not-to-use guidance. Siblings like lookup_endereco_cep or lookup_ibge_municipio exist but are not differentiated. The description implies usage for CEP lookups but does not help the agent choose between similar tools.

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