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

With no annotations, the description carries the burden of disclosing behavior. It makes the read-only nature clear through 'Look up' and enumerates the returned fields, including that street coverage is part of the result. It doesn't cover invalid input behavior or response shape, but for a simple lookup the core behavior is transparent.

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?

One sentence front-loads the verb and resource, gives a concrete example, and lists the output fields. No filler or redundancy.

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 one-parameter read-only lookup with no output schema, the description covers input format (with example) and output contents (place hierarchy and streets). The only gaps are lack of explicit differentiation from resolve_postal_code and any error/edge-case information, but the tool is otherwise self-explanatory.

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 cp7 parameter is already documented as 'Postal code NNNN-NNN'. The description adds only a concrete example and the CP7 term, which is helpful but does not substantially extend the schema's meaning.

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 opens with a specific verb ('Look up') and names the resource (Portuguese postal code CP7 with an example), then lists the returned information (localidade, concelho, distrito, streets). It is clear and concrete, though it does not explicitly differentiate itself from the sibling resolve_postal_code.

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 intended use is implied: use this when you have a CP7 like '1000-098' and want locality/district/street information. However, it gives no explicit when-to-use guidance, no prerequisites, and no comparison to resolve_postal_code or suggest_address.

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