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

Annotations already declare non-read-only, open-world, non-idempotent, non-destructive behavior, so the bar is lower; the description still adds real value by stating the callback window (within the hour during business hours), that it is free to the homeowner, and that a reference is returned. It does not mention failure modes such as an out-of-area ZIP rejection.

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?

Front-loaded with the core action and free of filler, but the second clause repeats the first ('A vetted local pro calls them back (a vetted local pro calls back within the hour during business hours)'), wasting a parenthetical on restatement. The prerequisite check sits appropriately at the end.

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?

No output schema exists, and the description compensates by saying a reference is returned plus what happens next. With consent requirements, the ZIP pre-check, and the callback promise all covered, the main remaining gap is what happens when the ZIP is outside the service area.

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?

Schema description coverage is 100%, so the schema already documents all seven parameters including formats and optionality. The description adds only an implicit consent/real-person constraint on name and phone, which is marginal beyond the structured data; baseline 3 applies.

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 verb and resource ('Book mobile mechanic') plus a geographic scope (Corpus Christi area) and the immediate outcome (a vetted pro calls back). It distinguishes itself from check_service_area by naming that sibling as a pre-check, though it says nothing about how it differs from get_service_info.

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?

Explicitly bounds usage to 'a real person who asked for it, with their consent' and routes the agent to check_service_area first when the ZIP is uncertain. That is clear when-to-use guidance, but the agent gets no guidance on when to prefer get_service_info or check_service_area over this tool.

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