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

The annotations already signal destructiveness and non-read-only behavior, and the description adds meaningful context beyond them: credit refund policy (full vs. proportional) and terminal states that make cancellation impossible. This gives the agent useful expectations about side effects and failure cases without contradicting the 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?

Three short sentences, each carrying necessary information: what the tool cancels, the financial consequence, and the non-cancellable states. The most important action is front-loaded, and there is no filler or repetition of the schema.

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 single-parameter cancellation tool with no output schema, the description covers the essential context: eligibility, credit impact, and invalid targets. The only minor gap is that it does not describe what the response looks like after a successful cancellation, but that is not critical given the tool's simplicity.

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 schema already fully documents the only parameter, job_id, including where it comes from ('returned by kleo_create_video'). The description adds no additional parameter semantics, but with 100% schema coverage, the baseline of 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 opens with a specific verb and resource ('Cancels a video') and narrows the scope to videos 'waiting or rendering,' which clearly distinguishes it from sibling tools like kleo_get_job and kleo_create_video. It also states the intended effect in concrete terms, so an agent can determine what this tool does without opening the schema.

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 description gives clear conditions for use: only waiting or rendering videos can be cancelled, and finished, failed, or already cancelled videos cannot be. It does not explicitly name an alternative tool, but the when/when-not guidance is concrete enough that an agent knows whether to attempt cancellation.

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