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

Annotations already declare destructiveHint=true, readOnlyHint=false, and idempotentHint=false, so the safety profile is covered. The description adds genuinely non-obvious behavior beyond that: money arriving after cancellation will no longer be matched to the request. It does not mention irreversibility, whether a second call errors (relevant given idempotentHint=false), or what state the request ends in.

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?

Two short sentences, front-loaded with the action and precondition. The bilingual Vietnamese/English duplication doubles the length, which is intentional for locale support but adds no new information.

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 one-parameter mutation tool, the description covers the eligibility precondition and the downstream consequence of cancelling. The only real gap is the return value / resulting state, which is not described despite there being no output 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?

With 100% schema description coverage, the single 'id' parameter is already documented with its pr_… format and pattern. The description adds no further constraint or interpretation of the ID, so the baseline of 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 specific verb ('cancel') and resource ('payment request') plus a scoping precondition ('that has not received any money'). This immediately separates it from create_payment_request, get_payment_request, and list_payment_requests in the sibling set.

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?

The eligible condition is stated clearly: only requests that have not received money may be cancelled, which implies the when-not case (received/paid requests are out of scope). It does not name an alternative tool or explain what to do when the request already has funds, 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.