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

Annotations already indicate non-read-only and non-destructive, but the description goes further by explaining the ownership check, deactivation (not deletion), and that historical events remain accessible via recent_alerts. This fully discloses side effects and aligns with the idempotent and non-destructive hints.

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 sentences, front-loaded with the core action, then the essential behavioral details. No wasted words.

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 simple one-parameter cancellation tool, the description covers the purpose, ownership constraint, and side effects. It omits explicit return/error behavior, but with no output schema and simple semantics, this is a minor gap.

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 fully documents the single 'id' parameter with a description ('returned by subscribe'), so the baseline is 3. The tool description adds the ownership context but does not add new parameter-level details beyond the schema.

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?

Clearly states the action ('Cancel a subscription by id'), specifies the resource, and distinguishes from sibling tools like subscribe and list_subscriptions. Ownership enforcement adds precision.

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?

Implies when to use (to cancel your own subscription) and enforces an ownership restriction, but does not explicitly name alternative tools or conditions for when not to use. The deactivation note clarifies the effect versus other operations.

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