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

The description discloses that the operation enforces ownership and performs a soft delete (deactivation) rather than a hard delete. This adds concrete behavioral detail beyond the annotations (e.g., destructiveHint=false) and informs the agent about the tool's side effects. The reference to historical events remaining available via recent_alerts is additional useful 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?

The description is two sentences, front-loaded with the action and followed by key behavioral constraints. Every sentence provides essential information without redundancy, making it highly concise and well-structured.

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 single-parameter tool with no output schema, the description covers the essential context: what it does, the ownership restriction, and the non-destructive effect with a pointer to related historical data. This is complete for the tool's complexity, and the annotations already cover idempotency and non-destructiveness.

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 already provides a complete description for 'id' ('Subscription id (uuid) returned by subscribe'), so the description adds little parameter-specific semantic value. Since schema coverage is 100%, the baseline of 3 is appropriate—the description only reiterates that cancellation is by id without adding new constraints.

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 opens with 'Cancel a subscription by id,' using a specific verb and resource with the method. This clearly distinguishes it from sibling tools like 'subscribe' and 'list_subscriptions.' The title reinforces the alert context.

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 explains the ownership constraint ('you can only cancel your own subscriptions'), giving clear context on when this tool applies. It also mentions the deactivation behavior and points to 'recent_alerts' for historical events, which helps with follow-up actions. However, it doesn't explicitly state alternatives or cases when not to use it, so it's not a perfect 5.

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