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

Annotations only declare readOnlyHint and openWorldHint, so the description carries the burden of explaining behavior and does add real context: it accounts for working hours, existing bookings, clean-up time and time off. The minimum-notice effect of for_client is also disclosed. It stops short of explaining result size/ordering beyond the schema's limit default.

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?

Three tight sentences, front-loaded with the core action, then behavioral coverage, then the one non-obvious parameter. No filler or repetition of the name.

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?

There is no output schema, but 'find open start times' plus the enumerated 'when' values and the 20-item limit default give an agent enough to call this correctly. The only gap, explicit non-overlap with pro_open_times, is a sibling-routing nuance rather than a calling blocker.

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 coverage is 75% (for_client has no description), and the description compensates by explaining that for_client applies the minimum-notice rule clients get, and by enumerating the accepted 'when' forms beyond the schema's bare 'Default week'. It adds genuine meaning over the structured fields.

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?

States a specific verb and resource: 'Find open start times for a service on the owner's calendar.' An agent knows exactly what the tool returns (open slots). However, it never differentiates itself from the sibling pro_open_times, which looks like the same capability viewed from another side, so routing between the two is left to inference.

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?

The accepted values for 'when' ('today', 'tomorrow', 'week', a date or range) and the for_client scenario give implicit usage context, and the minimum-notice note hints at the client-facing case. But there is no explicit statement of when to use this versus pro_open_times or my_calendar, so usage is implied rather than stated.

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