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

The description adds significant behavioral context beyond annotations: ownership is enforced, and the operation deactivates rather than deletes, preserving historical events. This clarifies the soft-delete behavior and the ownership precondition, which are not fully inferable from the annotations alone.

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, with two sentences. The core action is front-loaded ('Cancel a subscription by id'), and the second sentence efficiently conveys important caveats without 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 simple one-parameter mutation, the description covers the action, ownership enforcement, and the post-condition (deactivation, events preserved). It also ties to recent_alerts, providing a complete picture despite lacking an output schema or return type.

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 fully describes the id parameter, and the description adds a usage constraint (ownership) that affects parameter validity. While the baseline is 3 due to 100% schema coverage, the ownership note provides added semantic value 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 clearly states the tool's purpose: 'Cancel a subscription by id.' It uses a specific verb and resource, and distinguishes itself from siblings by noting ownership enforcement and the deactivation (not deletion) behavior, which sets it apart from 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?

The description provides clear context for when to use the tool ('Cancel a subscription by id') and notes ownership constraints, implying that only the owner can use it. It does not explicitly name alternatives or when-not scenarios, but the reference to recent_alerts and the deactivation behavior gives useful guidance on the tool's effect.

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