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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is partly covered. The description adds meaningful context that nothing was charged and no seat was held, which helps an agent understand the limited blast radius, though it does not describe the post-cancel session state or response.

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 description is two sentences, front-loads the primary operation, and immediately follows with the key exclusion. There is no redundant wording or tangential detail.

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 simple destructive cancellation tool with annotations covering idempotency and destructiveness and a fully described schema, the description supplies the essential usage boundary around paid versus unpaid sessions. It could say slightly more about what happens to the canceled session or the expected outcome, but nothing critical is missing for correct invocation.

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%, and the schema already documents the checkout id format and the optional UCP metadata including idempotency-key. The description adds no parameter-level meaning beyond the schema, so the baseline of 3 is appropriate.

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 gives a specific verb and resource: cancel an unpaid checkout session. It also scopes the operation to unpaid sessions and explicitly excludes paid bookings, so an agent can distinguish this from complete_checkout and update_checkout.

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 states the condition for use — an unpaid checkout session — and the exclusion — a paid booking cannot be canceled here and the customer must contact SYMONE. This gives explicit when-to-use and when-not-to-use guidance.

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