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

Annotations already flag destructiveHint=true and readOnlyHint=false, so the write/irreversible profile is covered structurally; the description adds the genuinely non-obvious constraint that cancellation is only valid before carrier collection. It stops short of saying whether a refund/void is triggered or what the response returns on failure.

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 front-loaded sentence with the eligibility rule in the first clause and the API equivalence as supporting detail. Nothing is padding.

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 destructive, open-world mutation with no output schema, the description covers eligibility but omits outcome (what happens to the label record, refunds, or tracking), failure modes, and required permissions. The annotations carry the safety signal, but the post-call behavior remains unstated.

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 (labelId, intentId) are already documented in the schema. The description adds no format, sourcing, or correlation-ID guidance beyond that, 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 specific verb ('Cancel') and resource ('a label') plus a scoping precondition ('the carrier has not collected yet') and anchors it to the equivalent REST endpoint. This separates it from read-side siblings like GetLabel and from RemakeLabel, though no sibling is named explicitly.

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 precondition 'has not collected yet' effectively states both when to use it and when it will fail, which is the key eligibility rule for a cancellation. It does not name alternatives (e.g., RemakeLabel for already-collected labels) or mention where to check collection status.

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