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

Annotations already declare destructiveHint=true and idempotentHint=true, so the bar is lower, but the description still earns credit by spelling out the concrete effect (checks and webhooks stop) and the irreversibility ('not refunded'), which the annotations alone do not convey. It stops short of saying what happens on an already-cancelled watch despite the idempotent hint.

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 compact sentences with the operational effect and the required inputs front-loaded; nearly every clause carries information. The opening 'Free:' label is the one piece of noise whose meaning is unclear.

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 2-parameter mutation with full schema coverage, no output schema and strong annotations, the description supplies the missing behavioral piece (checks/webhooks cease, no refund). Only the idempotent-when-already-cancelled behavior and the meaning of 'Free:' are left unexplained.

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%, with both properties documented in detail (whsec_... secret returned once, w_... watch_id from POST /v1/watch). The description only restates that these two values are required, adding no format or provenance detail beyond the schema, 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 and resource ('cancel a watch') and the immediate effect ('no further checks or webhooks'), so the agent knows exactly what operation is performed. It does not explicitly distinguish itself from siblings like watch_status or watch_mcp_server, and the leading 'Free:' token is ambiguous about what it qualifies.

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 consequences clause ('no further checks or webhooks; not refunded') implies this is the terminal teardown action and shouldn't be used casually, but the description never names an alternative (e.g. watch_status for inspecting, watch_mcp_server for changing) or states an explicit when-to-use condition.

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