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

Annotations already declare readOnlyHint, idempotentHint and closed-world scope, so the safety profile is covered. The description adds genuinely useful behavior beyond that: it discloses the response content ('returns yes/no and the nearest served town'), which matters because there is no output schema.

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 short sentences, the core question front-loaded, and the return value stated second. Nothing extraneous.

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 lookup with no output schema, the description covers the input domain and the return shape, and annotations cover the safety profile. Only the relationship to siblings (when to follow up with request_service) is left implicit.

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?

With only one parameter and 0% schema description coverage, the description must carry the load; it does clarify the input is a US ZIP code, and the schema's pattern enforces the 5-digit format. It adds no further meaning about accepted values beyond that.

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 states a specific check verb and resource ('Is a US ZIP code inside the Tempe service area?'), which is unambiguous on its own. It does not explicitly differentiate itself from siblings get_service_info or request_service, but the purpose is clear enough that an agent can distinguish it.

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?

Usage is only implied — an agent can infer this is the pre-check before request_service, but the description never says when to use it versus the siblings or what to do with the answer. No prerequisites or exclusions are stated.

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