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

Annotations already signal a destructive, idempotent, non-read operation. The description adds genuinely new behavioral context: it is a 'cooperative' cancel (a request, not a hard kill) and it describes billing/quota consequences ('queued work counts nothing; running work counts only if it produced a usable output'). That is value beyond 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?

Two tight sentences, front-loaded with the action and scope, followed by the billing consequence. Every sentence earns its place with no filler.

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 not be described, and annotations carry the safety profile. The description covers the cooperative nature and quota impact, leaving only minor gaps like failure modes when a running job cannot be cancelled.

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% and job_id is documented in the schema as 'A job id returned by a create tool.' The description adds no further parameter meaning, so the baseline of 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 (render job), and further qualifies the applicable states ('queued or running'). It's clear enough to distinguish from render.job.get and other render siblings, though it doesn't explicitly name a sibling it might be confused with.

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?

Implies usage by scoping to 'queued or running' jobs, which tells the agent when the tool applies. However, it gives no explicit when-not-to-use guidance, no prerequisites, and no alternatives if the job isn't cancellable.

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