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

Annotations indicate non-read-only, non-destructive, idempotent, and open-world hints. The description adds crucial context beyond these: ownership is enforced, the row is deactivated rather than deleted, and historical events remain available via recent_alerts. This meaningfully discloses side effects and safety posture without contradicting 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 two sentences long, front-loaded with the action, and contains no unnecessary words. Each sentence adds value: the first defines the operation, the second explains side effects and restrictions.

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 mutation tool, the description covers the key aspects: what it does, ownership, and persistence behavior. It omits return value or error handling details, but these are not critical for selecting and invoking the tool, especially given the rich annotations and straightforward schema.

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 parameter 'id' with a description ('Subscription id (uuid) returned by subscribe'). The description adds no new parameter details beyond what the schema already provides, so a baseline score of 3 is appropriate.

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 begins with a specific verb 'Cancel' and a clear resource, 'subscription by id.' It directly addresses the tool's purpose (unsubscribe) and differentiates from siblings by explicitly mentioning subscribe and recent_alerts, linking it to related operations.

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 clearly implies when to use this tool (to cancel a subscription) and includes an important constraint (ownership enforcement). However, it doesn't explicitly mention when not to use it or point to alternatives like list_subscriptions for finding subscription IDs, leaving some implicit guidance.

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