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

Goes well past the annotations (destructiveHint true) by disclosing the actual side effect — the diamond is returned to the wallet — plus ownership scoping, the state precondition (upcoming, not begun), and the refusal-with-reason failure modes. This is exactly the behavioral context an agent needs before invoking a destructive mutation.

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?

Three sentences, front-loaded with the action, with no repeated boilerplate. The closing instruction about naming the booking by label is behaviorally useful rather than filler, though the domain-specific flourish makes it slightly denser than strictly needed.

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 two-parameter mutation with no output schema, the description covers the side effect, eligibility, refusal cases, and the confirm-by-label interaction pattern. Nothing an agent needs in order to call it correctly or to explain the outcome 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 description coverage is 100%, so both parameters are already documented, and the schema's bookingId text mirrors the description's provenance note. The description adds no syntax, format, or constraint details beyond what the schema states, so 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 precise verb and resource — cancel one of the signed-in person's own upcoming bookings, by id obtained from my_bookings. The scope qualifiers (own, upcoming, canCancel true, the specific bookable types) cleanly separate it from cancel_registration and the booking-creation siblings.

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?

Gives explicit eligibility (must come from my_bookings where canCancel is true) and explicit refusal conditions (not theirs, already cancelled, already begun), which is strong when-to-use guidance. It never names the alternative sibling (e.g., move_booking) for a person who wants to reschedule instead of cancel, so it falls short of the top band.

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