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

Annotations already establish readOnly/non-destructive, and the description adds genuinely new behavior: results are in the studio's time zone, the searchable window starts tomorrow and caps at 90 days ahead with a 14-day-per-call limit. It also discloses that promotions are surfaced on returned times and applied automatically at booking, which is not derivable from 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?

Three compact sentences, front-loaded with the core definition and then the window constraints. The promotion sentence is slightly awkwardly phrased ('discount of the studio (percent, discounted price)') but every sentence carries information.

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 no output schema, the description does the necessary work of describing what comes back (start times, optionally a promotion with percent and discounted price) plus the timezone and window semantics. Only the ordering or count of returned slots is unstated, which is a minor gap for a 7-parameter read tool.

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 86%, so the schema already documents days, from_date, studio_id, employee_id and the time filters. The description largely restates the days limit and adds time-zone context, but says nothing about earliest_time/latest_time or the service_id/employee_id interaction beyond what the schema carries, so the 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?

The first sentence names a specific resource ('free start times') scoped to one service and one time zone, which is enough to distinguish it from get_studio and search_studios. It never explicitly contrasts itself with prepare_booking, but the verb+resource is unambiguous.

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 only implied: the date window (tomorrow to 90 days, max 14 per call) tells the agent how to call it, and the promotion sentence hints this precedes booking, but there is no explicit 'use this before prepare_booking' or 'do not use this to check a specific employee's schedule outside the window' guidance.

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