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

Annotations already declare readOnlyHint=false, openWorldHint=true, and idempotentHint=true, so the safety profile is covered. The description's real added value is the upload-completion precondition; 'Safe to call twice' merely restates idempotentHint rather than adding new behavioral detail such as error behavior on an incomplete upload or whether processing is asynchronous.

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 short sentences, front-loaded with the action and followed by the precondition, with zero filler. Every clause carries information an agent needs before calling.

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 mutation trigger with no output schema and one undocumented parameter, the description covers the precondition and idempotency but leaves the post-call path unstated: an agent does not learn whether to poll with wait_for_caption_job or call get_caption_job, nor what a call on a not-yet-uploaded job returns.

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% for the single job_id parameter, so the schema contributes nothing beyond the name. The description partially compensates by tying the job to create_caption_job, implying where job_id originates, but it never explicitly says job_id is the identifier returned by that sibling call.

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 ('Start processing') and resource ('a job'), and anchors it to a precise workflow position: after the video was PUT to the upload URL from create_caption_job. That sequencing is what separates it from siblings like get_caption_job, wait_for_caption_job, and create_caption_job without needing to open any 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?

Gives an explicit precondition for use: only after the video has been PUT to the upload URL issued by create_caption_job. It does not name the natural follow-up alternative (wait_for_caption_job) or say what to do if the upload has not completed, so the routing guidance is clear but not exhaustive.

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