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

readOnlyHint=true already tells the agent this is a safe read, and the description confirms a non-mutating list of time slots. It adds the scope constraint (group classes only) but says nothing about pagination, result ordering, or how empty/full months are represented beyond the includeUnavailable param in the 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?

Two sentences, zero waste, with the core purpose front-loaded and the REST endpoint noted as secondary reference. Nothing extraneous.

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 read-only list tool with fully documented parameters and no output schema, the description covers what is being returned (monthly class time slots) adequately. Minor omission: no hint about result shape or how 'unavailable' entries differ when includeUnavailable is set.

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 description coverage is 100%, so all four parameters (month, timezone, appointmentTypeID, includeUnavailable) are already documented in the schema with formats and behavior. The description adds no parameter-level meaning beyond that, 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?

States a specific verb ('List') and resource ('group class time slots') and scopes it to class-type appointment types, which meaningfully distinguishes it from sibling availability tools like acuity_availability_dates and acuity_availability_times. It never names those siblings explicitly, but the class-type qualifier carries the differentiation.

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 by the 'for class-type appointment types' qualifier, which tells the agent this is the availability variant for classes rather than times or dates. However, it never states when to prefer this over the sibling availability tools or any prerequisites beyond the schema's required fields.

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