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

Annotations supply destructiveHint=true, idempotentHint=true and readOnlyHint=false, and the description adds real context beyond them: entitlement tier, dual consent requirement, optimistic-concurrency revision matching, and an exact-intent confirmation step. It does not spell out what becomes unavailable after cancellation or whether it is reversible, which keeps it short of a 5.

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?

Front-loaded and only three sentences, but the revision guidance is stated twice ('using its current revision' and 'use its current revision when changing an existing record'), so one clause is redundant rather than earning its place.

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?

An output schema exists, so return values need no explanation, and the annotations already cover the safety profile. Combined with prerequisites, consent and concurrency semantics, the agent has enough to invoke it correctly, with only the post-cancel state left unspecified.

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 0%, so the description must carry the load, and it does: idempotency_key is characterized as stable, expected_version as the record's current revision, and the confirmation requirement maps to the nested ConfirmInput. project_id is never explained, but it is self-evident.

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 a scoped resource (an existing cancellable internal action), and adds the mechanism (using its current revision). It is distinct from siblings like execute_action, approve_action and retry_action, though it never names an alternative explicitly to sharpen the boundary.

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?

Gives concrete preconditions for use: Startup tier or higher, both read and write consent, a stable idempotency key, and exact-intent confirmation. It lacks any explicit when-not or comparison to sibling actions (e.g., retry_action vs cancel_action), so the agent gets context but not disambiguation.

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