Lookup Brazilian Address (CEP)

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

Annotations indicate readOnlyHint=true and idempotentHint=true, so the behavior is safe. The description adds that it returns specific address components and timezone, which is useful but largely echoes the parameter description in the input schema. No contradictions; the description aligns with annotations and provides moderate extra context beyond the schema.

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?

A single sentence that clearly states the purpose and return data, followed by a brief source attribution. No extraneous information; every part adds value. The description is front-loaded and efficient.

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 tool has only one required parameter and an output schema (not shown but implied). The description covers the core functionality, input format, and output fields. It is sufficient for an agent to decide whether to use this tool and how to invoke 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?

Schema coverage is 100% with a single parameter 'cep' that already includes a detailed description (format, examples, return fields). The tool description essentially reiterates the schema info ('8-digit CEP postal code'), adding only the phrase 'with or without dash' which is already in the schema. Baseline of 3 is appropriate as the schema carries the semantic burden.

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 explicitly states the verb 'Look up' and the resource 'Brazilian address by 8-digit CEP postal code', and mentions the return fields (street, neighborhood, city, state, coordinates, timezone). Title reinforces the specific country (Brazil). It clearly distinguishes from other address tools by specifying the CEP system.

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 explains what the tool does and implies its use for Brazilian addresses via CEP, but it does not provide explicit guidance on when to use this tool versus alternatives (e.g., other address lookup tools like address.postal.lookup or gov.brasilapi.ddd). No exclusions or when-not-to-use context are provided.

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