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

With no annotations, the description carries the full burden, but it is a read-only lookup by nature. It usefully discloses the returned fields and the per-call price ($0.003), which is real context beyond the schema. It does not say what happens for an invalid or unknown CEP, nor whether results are cached or rate-limited.

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?

Very short and front-loaded: the resource and returned fields come first, the price last. It is a telegraphic fragment rather than full prose, but every token earns its place.

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 single-parameter read lookup with no output schema, the description adequately enumerates the response payload and the cost, which is the key operational fact. Only error/edge-case behavior is left unspecified.

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 'cep' parameter is fully documented in the schema (8 digits, optional hyphen), so the description adds no parameter detail. Baseline 3 applies when the schema does the heavy lifting.

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?

States a specific verb+resource: lookup a Brazilian address by CEP, and enumerates exactly what comes back (street, neighborhood, city, state, IBGE codes, coordinates). This clearly distinguishes it from siblings like validate_identifier or lookup_bank, though it never names an alternative 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?

There is no when-to-use guidance, no prerequisites, and no mention of alternatives or when a different lookup tool (e.g. validate_identifier) would be preferred. The agent is left to infer the context entirely.

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