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

Annotations already cover idempotency (idempotentHint=true) and safety (destructiveHint=false), but the description adds substantial context beyond them: the request may not stop upstream provider work, cost is not refunded, the call is safe to retry because terminal jobs report their state, bearer key is required, and the specific error codes. That is unusually rich disclosure for a mutation tool.

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 with purpose and the key usage constraint, and most sentences carry distinct information. However, the return values are stated twice ('Returns whether the request was accepted...' and 'Returns: Cancellation outcome envelope...'), which is mild redundancy.

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?

Covers usage, caveats, auth, retry semantics, and error codes, and an output schema exists so return-shape explanation is not strictly required. The duplicated return description is the only thing keeping this from being fully tight, but nothing an agent needs to call it correctly 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?

Schema description coverage is 100% and the job_id description already includes the pointer to hydracept_jobs_find for unknown ids. The description adds no additional parameter-level meaning, so the baseline 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 (one job), and explicitly bounds the scope by ruling out the near-miss interpretation ('stopping a local polling loop is not a cancellation'). An agent can distinguish this from siblings like hydracept_job_status or hydracept_submit_job without opening 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 when-to-use condition ('only when the user explicitly asks to cancel the job itself') and a when-not ('stopping a local polling loop is not a cancellation'). This is exactly the routing guidance an agent needs to avoid mis-triggering on a stop-polling intent.

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