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

Annotations already declare idempotentHint=true, destructiveHint=false and readOnlyHint=false, so the description doesn't need to restate safety. It goes further by disclosing the concrete consequence — it 'stops future change checks and charges' — and confirms it is free and that a repeat call returns the same cancelled state, which is real operational context.

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?

Three short sentences with zero waste: the action and identifier come first, followed by cost/idempotency, then sibling routing. Every clause earns its place.

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 two-parameter mutation with annotations, a full schema and an output schema, the description covers effect, cost, idempotency and alternatives. Minor gaps remain around whether in-flight checks are completed before cancellation takes effect.

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 coverage is 100% and both parameters carry their own descriptions, including where to obtain watch_id. The description's mention of watch_id adds no format or validation detail beyond the schema, 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 and resource — 'Cancel one of your standing URL watches by watch_id' — and explicitly distinguishes itself from watch_list (view) and check_url_changes (create). An agent can route correctly without opening the 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?

Names both relevant alternatives with their roles ('Your watches: watch_list. Create one: check_url_changes'), which gives clear routing context. It stops short of stating exclusions or prerequisites (e.g., that the watch must not already be cancelled).

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