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

Annotations only say read-only/idempotent/non-destructive; the description adds substantive behavior: windows whose last start has passed on the studio's clock are excluded, results are capped at 8 bookable pages of at most 10, site and session-type lookups are cached, and omitted sessionTypeIds fall back to the first 8 online-bookable types. These are operational facts an agent cannot derive from the annotations or schema.

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?

Purpose is front-loaded and the definitional sentence about windows is well placed before the output-field explanation. It is dense but nearly every sentence adds information; the closing Mindbody-call/pagination sentence is the most implementation-heavy and could be trimmed slightly.

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, so the description carries the full burden of explaining return values, and it does so field by field (window count, first start, lastStart, start minutes, estimatedSlots). Combined with exclusion rules, caps, and defaults, an agent has everything needed to call it correctly and interpret results.

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 baseline is 3, but the description adds meaning the schema lacks: it explains that results are grouped by session type and staff (which determines what 'limit' counts), defines lastStart and estimatedSlots, and warns that wide queries need sessionTypeIds or staffIds. The date-range and staff/location caps themselves remain schema-only.

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 opening clause states a specific verb and resource: 'Where a client can still be booked: open availability windows grouped by session type and staff.' It then defines what a window is ('a stretch of free time, not one slot'), which prevents the common misreading of the result as individual bookable slots and separates it from booking-lookup siblings like get_staff_appointments.

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?

It gives a clear use condition (finding bookable availability) plus explicit exclusions: it does not report historical appointment statuses, no-shows, or booked hours, which steers agents elsewhere for those needs. It also states a query-scope rule ('must pass session types or staff rather than expecting an unbounded scan'). It stops short of naming the specific sibling to use for historical or booked data.

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