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 genuinely new behavioral context: this is a free referral service rather than the mechanic itself, which changes how an agent should present the data, and it lists the categories of facts returned in the absence of an 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?

A single front-loaded sentence with a colon-delimited list of covered facts, plus one imperative routing clause. Nothing is wasted, though the enumerated list is dense enough that readability suffers slightly.

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 zero-parameter, read-only lookup with no output schema, the definition supplies what an agent needs: what is returned (towns, prices, hours, response time, languages, phone), the nature of the provider (referral service), and when to call it. Nothing material is missing.

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; baseline 4 applies. No misleading parameter claims are made.

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 (facts about AR Mobile Mechanic, a free referral service in Phoenix) and enumerates exactly what it covers: towns served, prices, hours, response time, languages, phone. That is more precise than any sibling, though it never names check_service_area or request_service explicitly, so the routing to siblings is only implied.

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 when-to-use trigger and implicitly steers the agent away from request_service for read-only information. It stops short of stating exclusions, such as when check_service_area is the better fit.

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