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

Annotations already indicate non-read-only, non-destructive, idempotent behavior. The description adds valuable context: ownership enforcement ('only cancel your own subscriptions') and the soft-delete mechanism ('deactivated not deleted'). This explains why destructiveHint is false and gives insight into side effects and data retention 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 concise (3 sentences) and front-loaded with the core action. Each subsequent sentence adds a necessary behavioral detail (ownership enforcement, soft-delete) without waste or fluff.

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 tool with no output schema, the description covers the key aspects: what it does, who can use it, side effects (deactivation vs deletion), and downstream availability via recent_alerts. Combined with rich annotations (idempotent, non-destructive), it is complete for its scope.

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: it identifies the id as a uuid returned by subscribe. The description adds no additional parameter-level meaning beyond what the schema provides, so the 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 opens with a specific verb and resource: 'Cancel a subscription by id.' It clearly distinguishes from siblings like subscribe (creation) and list_subscriptions (listing) by focusing on cancellation. Additional details about ownership and soft-delete further clarify its unique role.

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?

Clear context is provided: you cancel a subscription by id, and you can only cancel your own. The soft-delete note mentions historical events remain available via recent_alerts, giving a hint of complementary tooling. However, it does not explicitly state when not to use this tool or name alternatives like list_subscriptions for finding a subscription id.

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