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

Beyond the annotations (idempotentHint, destructiveHint), the description discloses the soft-delete behavior and ownership restriction. This adds meaningful context about the side effects and data preservation, which annotations alone don't fully convey.

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 concise sentences front-load the action ('Cancel a subscription by id') then add key nuances. Every sentence adds value with no redundancy.

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 one-parameter tool with no output schema, the description covers the essential behavior: ownership, deactivation, and historical data preservation. It references recent_alerts, providing sufficient operational context for an agent.

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?

Schema coverage is 100% with the id parameter already described as 'Subscription id (uuid) returned by subscribe.' The description only says 'by id' without adding further parameter detail, so it meets the baseline but doesn't enhance semantics.

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 states 'Cancel a subscription by id' with a specific verb and resource. It distinguishes from siblings by clarifying ownership enforcement and the deactivation-vs-deletion behavior, making its purpose unambiguous compared to subscribe and list_subscriptions.

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?

It provides clear context: ownership is enforced, and cancellation deactivates rather than deletes, preserving history via recent_alerts. This implies when to use it and what to expect, though it doesn't explicitly name alternative tools or 'when not to use' scenarios.

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