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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely useful behavior beyond that: results are in time order, driven by working hours, breaks, time off, and per-service duration/buffer, and it requires a Cotlet API key with app access.

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 core scope is front-loaded, but the description repeats itself: 'working hours, breaks and time off' appears twice and 'free start times for a service on one day' is restated in the second sentence. Two sentences of the same content could be condensed into one.

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 usefully explains the return value (free start times in time order) and the scheduling rules behind it, and annotations cover the safety profile. An agent has enough to invoke it correctly, though prerequisites (a valid service_id from booksy_list_services) are only implied via the schema.

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 schema already documents all three parameters including staff_id's default and service_id's origin. The description only restates the one-service/one-day scope and the optional staff narrowing, adding marginal meaning beyond the schema. 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 description states a specific action and scope clearly: it returns free start times for one service on one day. An agent can tell this is a read/availability tool distinct from booksy_create_appointment or booksy_list_appointments, though it never names a sibling to contrast with.

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 implied usage context ('Limit it to one staff member or leave it open to anyone who offers the service') and an auth note, but never states when to prefer this over alternatives like booksy_list_appointments or how it pairs with creating an appointment. Context is present but no explicit when/when-not.

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