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

Description discloses the concrete behavioral consequence—invalidating the fill link so the human can no longer submit a value—which goes beyond the destructiveHint annotation. It does not contradict annotations.

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 concise sentences with no fluff; the purpose, effect, and usage condition are all communicated efficiently.

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 one-parameter destructive/idempotent operation, the description fully conveys what the tool does and when to use it. Return values are not required since an output schema exists.

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?

The single parameter is fully covered by the schema ('Credential-request ID'), and the description only restates that the action is by ID. Since schema coverage is high, the description adds little additional parameter meaning, so 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?

Description states a specific verb ('cancel'), a specific resource ('credential request'), and the key effect ('invalidates the single-use fill link'), clearly distinguishing it from sibling tools like create, fill, and status.

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?

Explicitly states when to use the tool: 'when the request is no longer needed or was created in error.' This gives clear usage context and no alternative is needed given the cancellation purpose.

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