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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), so the bar is lower, yet the description still adds meaningful context: this is a free third-party referral service rather than the mechanic itself, and it enumerates the fields returned. It does not cover freshness of prices/hours or any response limits, which keeps it below 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?

One descriptive sentence front-loads the subject, followed by a single imperative call to action. The field list earns its place because no output schema exists to communicate what comes back.

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 full informational burden, and it does: it names the entity, its nature as a referral service, the data returned, and when to invoke it.

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 the schema carries nothing to explain; the description's enumeration of return fields is the closest thing to parameter/scope semantics. Baseline 4 applies for a no-parameter tool.

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 concrete verb-and-resource: it returns facts (towns served, prices, hours, response time, languages, phone) about Boise Car Fix, a mobile-mechanic referral service. An agent can tell it is an informational lookup, though it never explicitly contrasts itself with the overlapping 'check_service_area' sibling, which also concerns coverage/towns.

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 sequencing rule that positions it upstream of request_service. There is no explicit when-not guidance or named alternative, but the context for use is unambiguous.

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