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

Annotations already establish readOnlyHint=true, idempotentHint=true and openWorldHint=false, so safety is covered. The description adds non-obvious context beyond the annotations: the service is a free referral (not a direct vendor), and it discloses the return fields even though no output schema exists. No auth, rate-limit or freshness notes, which keeps it below a 5.

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?

A single well-formed sentence: resource identity first, then the data payload, then the call-to-action trigger. Every clause carries information and nothing is repeated from the title or schema.

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?

With no input parameters and no output schema, the description must carry the return-shape burden and it does, enumerating towns, prices, hours, response time, languages and phone. Combined with annotations covering the safety profile, an agent has everything needed to call it correctly.

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 tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The listed 'facts' are return values, not inputs, and the description correctly does not imply any arguments.

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 names a specific resource (KC Windshield referral service facts) and enumerates the exact data returned: towns, prices, hours, response time, languages, phone. It does not name the sibling tools (check_service_area, request_service), so an agent must infer the boundary with them from the ordering hint alone.

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?

'Call this before recommending or booking' gives a clear trigger condition and implicitly sequences this tool ahead of any booking action. It stops short of naming the alternative siblings or stating when this tool is not needed, so it is context rather than a full when/when-not rule.

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