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

Annotations indicate a mutation (readOnlyHint=false) that is idempotent and non-destructive. The description adds crucial behavioral details: ownership enforcement, row deactivation rather than deletion, and preservation of historical events. No contradictions with 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 three sentences with no wasted words. The first sentence states the action and parameter, the second adds ownership constraint, the third explains post-action state. Information is front-loaded and each sentence 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?

Given the tool's simplicity (one parameter, no output schema), the description covers all necessary aspects: action, constraints, side effects, and links to related tools (subscribe, recent_alerts). It is fully sufficient for correct selection and invocation.

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 input schema has 100% coverage with a clear description for the 'id' parameter. The description adds no additional semantic information beyond stating 'by id', which is redundant. The baseline of 3 is appropriate since the schema already documents the parameter adequately.

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 states the action 'Cancel a subscription by id' and explains the behavioral effect (deactivation, not deletion). It distinguishes itself from siblings like 'subscribe' and 'list_subscriptions' by specifying what it does and its ownership constraint.

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 description provides clear context: 'Ownership is enforced — you can only cancel your own subscriptions.' It also implies when not to use it (not for others' subscriptions) and references alternative tool 'recent_alerts' for historical data, but does not explicitly list when to avoid using this tool.

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