lookup_ddd

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

This is a read-only lookup tool with no annotations provided, so the description carries the burden. It states what it returns (state and municipalities) but doesn't disclose behavior for invalid/unknown DDD codes, error handling, or formatting of the returned list. For a read-only tool, this is adequate but not rich.

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?

Two concise sentences that pack purpose and return-value summary without waste. Front-loaded with the key action and resource. Slightly redundant with the schema's parameter description, but overall 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?

For a simple single-parameter read-only lookup with a full input schema and an output schema present, the description is reasonably complete. It explains what's returned (UF + municipalities). It doesn't need to over-explain given the output schema handles return details.

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 description coverage is 100%, so the 'ddd' parameter is fully documented as a 2-digit area code with an example. The description adds minimal extra meaning beyond confirming the parameter drives state/municipality lookup. Baseline 3 is appropriate given full schema coverage.

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 uses a specific verb ('Look up') with a clear resource (Brazilian area code / DDD) and defines the output (state UF + municipalities). It distinguishes from siblings like lookup_cep, lookup_cnpj, and list_municipalities, though it doesn't explicitly name alternatives.

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 implicitly conveys usage context (looking up DDD area codes for Brazilian regions) but provides no explicit when-to-use guidance or notable exclusions/alternatives. Context is inferable from the siblings, but no alternative tools are named.

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