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

Annotations already declare readOnly, idempotent, non-destructive, closed-world. The description adds genuinely useful behavior beyond that: a time is not held until the person books it, and every result carries a booking_url that opens a prefilled lightbox. That holding/booking semantics is real added value not in the annotations.

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 sentences, front-loaded with the core capability, followed by return-content and booking-semantics details. Every sentence is relevant, though the lightbox mechanics sentence is slightly verbose.

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 an output schema present and full schema coverage, the description needn't explain return values, yet it still summarizes them (practitioners, prices, booking_url). Combined with the holding caveat, an agent has enough to call it correctly; only explicit sibling routing 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?

Schema coverage is 100% with rich per-parameter descriptions (including provenance hints like 'option_id get_treatment returns'). The description only restates option_id, clinic_id, and the 7-day cap, so it adds little beyond the fully documented schema – baseline 3.

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 (find) and resource (free times) with clear scope: one option_id at a clinic, single date or up to 7 days. It distinguishes the resource from find_free_days and find_practitioners by clarifying it returns times plus practitioners and prices, though it never names those siblings explicitly.

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?

Usage is implied through the parameters (clinic_id, option_id) and the note that clinic_id comes from find_clinics, but there is no explicit when-to-use/when-not guidance nor a named alternative such as find_free_days for day-level availability.

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