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

Annotations already declare readOnly/destructive/openWorld, yet the description adds real behavioral context beyond them: card details are never returned, the last-appointment field ignores cancelled and no-show bookings (matching the Client insights report), pages cap at 500 with a next_cursor round-trip, and it states the Cotlet API key requirement. That is exactly the extra disclosure the annotations do not provide.

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?

The most important facts (what is listed, pagination, auth) are front-loaded and the description is well sized. It loses a point for redundancy: the opening sentence and the following sentence restate the same field list, which is wasted space.

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 carries the burden of describing returns, and it does so thoroughly: contact details, last appointment date, marketing consent, plus edge-case semantics and the card-data exclusion. Pagination and auth are also covered, so nothing an agent needs to call this correctly 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%, so the parameters are already documented and the baseline is 3. The description adds genuine semantic value beyond the schema by explaining what last_appointment_before really means ('clients who have not been in since a date') rather than just restating the field.

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 description states a specific verb and resource ('Lists clients, A to Z, with contact details, their last appointment date and marketing consent'), so the agent immediately knows what the tool returns. However, it never names or differentiates itself from sibling reads such as fresha_get_client or fresha_list_appointments, so the comparison work is left to the agent.

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 an explicit conditional use case: 'Use last_appointment_before to find clients who have not been in since a date.' That is clear scenario guidance, but there are no exclusions and no mention of when to prefer this over fresha_get_client or fresha_add_client, so it stops short of full routing guidance.

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