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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real behavioral context the annotations don't: it discloses the return shape (per-day open-slot count plus first start/last end time), the 14-day window, that skipped days mean no availability, and that names are omitted.

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 use-case trigger and dense but purposeful. The second sentence is somewhat run-on in packing return shape, window, and exclusions together, but no sentence is wasted.

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?

For a single-parameter read-only tool with an output schema and full annotation coverage, the description supplies everything an agent needs: when to use, what is returned, the time window, and the booking exclusion. Nothing material 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% and the single gymId parameter is fully documented in the schema, so the description adds no parameter-level detail. Baseline 3 applies when the schema does the heavy lifting.

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 free session slots') and scopes it to gym availability. It is clearly distinguishable from siblings like get_gym_schedule_summary by emphasizing openings/booked days rather than a schedule, and the closing 'Not for booking a session' removes ambiguity.

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?

Opens with an explicit when-to-use trigger ('when someone asks when their gym has free slots... or which coming days are fully booked') and states a when-not ('Not for booking a session'). It does not name a specific alternative sibling tool, but the usage context is clear.

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