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

The description goes beyond annotations by explaining that the subscription is deactivated (not deleted) and historical events remain accessible via 'recent_alerts'. Annotations already indicate idempotent and non-destructive behavior, which the description supports.

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 sentences, front-loaded with the main action, no wasted words. Every sentence adds essential information.

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?

The description covers the tool's effect (deactivation, not deletion) and ownership constraint. It lacks acknowledgement of success/error responses or idempotency behavior, but given the simple single-parameter tool and annotation coverage, it is largely complete.

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 already provides a description for 'id' ('Subscription id (uuid) returned by subscribe'), which matches the description's mention of 'Subscription id (uuid) returned by subscribe.' The description adds no additional parameter semantics beyond the schema.

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 explicitly states 'Cancel a subscription by id', using a specific verb and resource. It distinguishes itself from the sibling 'subscribe' tool by mentioning ownership enforcement and the effect on historical events.

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 enforcement ('you can only cancel your own subscriptions') and the result (deactivation, not deletion). However, it does not explicitly state when not to use this tool or suggest alternatives like 'list_subscriptions' to find the id.

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