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

Goes well beyond the annotations (readOnly=false, destructive=false, openWorld=true) by disclosing the confirmation gate ('By default you confirm each call'), the external reach ('Reaches other people: confirm with the user before each call'), the payment-policy side effect, and the required Cotlet API key. These are real behavioral consequences an agent must know before invoking.

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 core action and scoping in the first two sentences, then follows with constraints. A few sentences ('Cancels one appointment', the confirm-toggle note) are slightly redundant but each carries a distinct constraint, so the size is warranted.

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 mutation tool with no output schema, the description covers the failure mode (past appointments), series scoping, payment-policy behavior, client notification, confirmation requirement, and auth needs. Nothing an agent needs to call it 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 baseline is 3, but the description adds genuine meaning: the 'reason' must come from the user's managed cancellation reasons and the 'scope' enum picks appointment vs whole series. That is more than the schema alone conveys.

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 ('Cancel a current or future appointment') and clarifies the boundary ('Cancels one appointment', 'Fresha only cancels appointments that start in the future'). It distinguishes the action from marking a no-show, though it doesn't explicitly contrast against fresha siblings like reschedule_appointment or create_appointment.

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 explicit when-not guidance ('a past one fails; mark it as a no-show in the app instead') and the condition selecting series scope ('For a repeating series, scope picks this appointment or the whole series'). Both the exclusion and the alternative action are named, leaving little to inference.

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