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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds useful context like the data source, per-call price, and HTTP verb, but does not disclose response format details, pagination behavior, or country handling beyond what the schema already notes.

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 compact, front-loaded sentence communicates the core operation, result type, source, cost, and endpoint with no filler. Every element 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 simple two-parameter lookup with no output schema, the description provides the essential return concept and enough constraints to call it correctly, especially with the schema covering defaults. The only notable gap is the absence of explicit differentiation from sibling geocoding tools.

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 description coverage is 100%, with both code and country having descriptions and examples, so the schema carries the parameter-documentation burden. The description does not add parameter-specific meaning beyond the generic postal-code-to-place transformation.

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 clearly states the verb-resource pair ('Postal code lookup') and the expected transformation ('ZIP/postal code → place(s) & coordinates'), which distinguishes it from address geocoding or reverse geocoding. It does not explicitly contrast itself with sibling tools, but the input type is sufficiently clear.

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 implies when to use it: when the user supplies a postal code and wants places/coordinates. However, it gives no explicit exclusions or alternative tool routing, such as when v1_geocode or v1_reverse_geocode might be more appropriate, so the guidance is inferred rather than stated.

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