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

Annotations already declare readOnly/destructive/openWorld, so the read-safety bar is met. The description adds genuine context the annotations don't: the default broadening to all qualifying employees when staff_id is omitted, the sorted ordering, and the auth prerequisite ('Needs the user's Cotlet API key with access to this app').

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 purpose and workflow, and each sentence adds something (filtering, return shape, default behavior, follow-up, auth). Mild redundancy between the first two sentences, both restating 'a service in a date range'.

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 fully covers the return ('open start times, earliest first, each with the employees free'), the default staff behavior, and the auth requirement — everything an agent needs to invoke and use the result.

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 100%, so the schema already documents all five parameters including defaults. The description reinforces the service/date-range/staff_id semantics and the staff_id-absent behavior but adds little syntax or format detail beyond the schema. Baseline 3 is appropriate.

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+resource (find open times for a service) with scope (date range, employees who can perform it). The return shape ('open start times ... earliest first, each with the employees free at that time') makes it unmistakable versus booking siblings, and it names book_appointment to differentiate.

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?

Clearly frames the workflow: 'Use a start and staff_id from the result with book_appointment' routes the agent to the follow-up tool, and 'Without staff_id it searches every employee' explains the default selection. No explicit when-not-to-use or exclusion, so it stops short of a 5.

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