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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds one genuinely useful behavioral fact — that this is a referral service, not the mechanic itself — but says nothing about freshness of the data or rate limits. Adequate against an annotated read-only tool.

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 plus one call-to-action, with the subject and scope front-loaded. No filler, and the enumerated data points are the substance rather than padding.

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 output schema and no parameters, the description carries the burden of telling the agent what comes back, and it does so by listing the returned fields. It does not explain format or whether results are static, but for a trivial zero-arg info lookup this is nearly complete.

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, which is the baseline 4 case. The description correctly implies no input is needed and instead describes the content of the response.

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?

Names a specific resource (facts about Phoenix Mobile Mechanic Co) and enumerates exactly what those facts cover: towns served, prices, hours, response time, languages, phone. It also clarifies the entity is a free referral service, which distinguishes it from check_service_area and request_service.

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 clear sequencing guidance relative to the booking-oriented sibling. It stops short of explicitly naming check_service_area or request_service as the alternatives, so routing relies on inference.

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