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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is covered. The description adds genuine behavioral context beyond them: the pipeline stops driving the phone between steps, and a not-yet-started job merely no-ops, which explains the graded effect of cancellation by state and is consistent with the idempotent hint.

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 sentences, zero filler, and the core action plus platform scope are front-loaded ahead of the edge-case behavior. Every clause carries 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?

There is no output schema, but the description covers the input requirement, the affected states, and the runtime consequence of cancelling, which is sufficient for a one-parameter mutation tool. It could still clarify whether the cancelled submission record remains queryable afterward, but nothing critical is missing.

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 a single parameter and 100% schema description coverage, the schema already documents submission_id. The description only adds the note that the ID applies 'on any platform', which lightly clarifies that the identifier is not platform-scoped; no additional format or constraint detail is offered.

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) plus resource (video submission) and enumerates the platforms it applies to, so an agent knows exactly what the call does. It stops short of distinguishing itself from the sibling delete-submission-tool, leaving the cancel-vs-delete boundary to inference.

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?

It implies the applicable states (scheduled, queued, in-flight) and therefore when the tool is meaningful, which is more than nothing. But it never names the alternative (delete-submission-tool) or states when to use one over the other, so routing guidance is implied rather than explicit.

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