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

The description adds significant behavioral context beyond the annotations: it explains that the row is deactivated (not deleted) and that historical events remain available via recent_alerts. This directly addresses the mutation's side effects and aligns with the destructiveHint=false and idempotentHint=true annotations, enriching the agent's understanding.

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 extremely concise—two sentences—with the action stated first, followed by ownership enforcement and behavioral effects. Every sentence adds value, and the structure is well-organized.

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 tool with one parameter and no output schema, the description covers the essential context: the cancellation action, ownership constraint, and the deactivation behavior. It does not explain return values, but that is not critical for a mutation tool with these annotations. Overall, it is complete enough for an agent to invoke it correctly.

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 schema already provides 100% coverage of the parameter description ('Subscription id (uuid) returned by subscribe'). The tool description adds no additional parameter semantics, so the baseline score of 3 applies.

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.' It uses a specific verb (cancel) and resource (subscription), and distinguishes itself from siblings like subscribe and list_subscriptions by focusing on cancellation.

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.' This tells the agent when it is appropriate to use the tool and sets a precondition. It does not explicitly name alternatives or when not to use it, but the guidance is sufficient for this simple tool.

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