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

With no annotations, the description carries the behavioral disclosure burden. It clearly states the output fields (street, localidade, concelho, distrito, cp7) and the special cp7-null behavior. This provides meaningful operational information beyond the input schema, though it omits details like empty-result behavior.

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?

Four tightly written sentences: one overview, one input format with examples, one output description, and one conditional handoff to a sibling. Every sentence adds distinct value with no filler or repetition.

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?

Given the low parameter count and absence of an output schema, the description is nearly complete: it explains input variants, expected output fields, and a routing condition. A minor gap is that art_id is referenced as an input to resolve_postal_code but is not explicitly listed among the suggestion fields, so the agent must infer it comes from the response.

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%, so the baseline is 3. The description goes beyond the schema by giving real examples ('av liberdade lisboa 196', '1000-098') and explaining how q can represent different forms, including locality and door number. It does not add much for count, but the schema already documents it.

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 begins with a specific verb and resource: 'Autocomplete a Portuguese address or postal code.' It also differentiates from the sibling tool by explaining the condition under which resolve_postal_code should be used instead.

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?

It explicitly tells the agent when to hand off to resolve_postal_code: 'When cp7 is null ... call resolve_postal_code with art_id and the door number.' It also gives concrete input examples for both address text and postal codes. It does not fully distinguish from postal_code_info, but the core usage context is clear.

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