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

Annotations already indicate idempotent and non-destructive behavior. The description adds valuable context beyond these hints: ownership is enforced (only own subscriptions can be cancelled), and the row is deactivated rather than deleted, preserving historical events via recent_alerts. This transparency helps the agent understand the full lifecycle of the operation.

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 includes only necessary constraints and behavioral details. No wasted words.

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 single-parameter tool with no output schema and supportive annotations, the description covers purpose, usage constraints, and data lifecycle. It gives the agent enough information to invoke the tool correctly and understand the consequences.

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 fully describes the only parameter (id as a uuid returned by subscribe), and the description merely restates 'by id' without adding further semantic detail. With 100% schema coverage, the description does not need to compensate, so the baseline 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') and identifies the resource (subscription). It distinguishes itself from sibling tools like subscribe and list_subscriptions by focusing on cancellation, making the purpose unambiguous.

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 for when to use the tool, including ownership enforcement and the deactivation behavior. It references recent_alerts for historical events, which is helpful, but it does not explicitly name alternatives for viewing or creating subscriptions (e.g., list_subscriptions, subscribe).

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