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

Beyond the annotations, it explains idempotency, identical errors for foreign versus nonexistent ids, freeing a watch-limit slot, never being billed, blank-key signup behavior, and plane-session ownership. This is rich behavioral disclosure and does not contradict 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?

The description is dense and mostly information-bearing, with no filler. The 'WHEN' phrasing is slightly awkward and the final plane-session sentence is cryptic, but overall the structure is acceptable.

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?

Despite having no output schema, it provides an input/output example, error semantics, idempotency, side effects, billing behavior, auth guidance, and a plane-session caveat. An agent has enough context to invoke and interpret the call correctly.

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 watch_id parameter is given real meaning by referencing where it comes from, showing an example mapping, and explaining error behavior. The plane_api_key parameter has schema-level description coverage, so the description does not need to fully repeat it.

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 clearly identifies the action as cancelling a watch that should stop firing, and references the watch id returned by watch_company or list_watches. The example makes the operation unambiguous and distinguishes it from creating or listing watches.

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 opening phrase 'WHEN a watch should stop firing' gives a direct condition for using the tool. It also clarifies ownership requirements by saying an id that is not one of your watches is an error, but it does not explicitly name a sibling alternative to avoid.

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