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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, giving the agent the safety profile. The description adds the constraint that only one's own open requests can be canceled, which is useful behavioral context beyond the annotations, though it doesn't cover idempotency, permissions, or cancellation effects.

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?

A single, well-structured sentence that front-loads the core action and includes the key qualifier without any filler.

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 two-parameter mutation tool with full schema coverage and annotations covering the safety profile, the description is largely complete. It conveys ownership and state constraints, though it could clarify what happens to the request after cancellation (e.g., becomes void) or any side effects.

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 both parameters (api_token and request_id) are fully documented in the schema. The description's 'your own open payment request' aligns with the request_id schema description, adding minimal value beyond what's already provided. Baseline 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 states a specific verb (cancel) and resource (payment request) with an ownership/state qualifier ('your own open'). It distinguishes itself from siblings like request_payment, pay, and list_payment_requests, though it doesn't explicitly name an alternative path.

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 phrase 'your own open' implies when this tool is applicable (only for your own requests that are still open), which is useful context, but no explicit when-to-use vs. when-not-to-use guidance or alternatives are given.

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