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

Beyond the annotations (idempotent, non-destructive, mutating), the description explains the soft-delete behavior ('deactivated, not deleted') and the impact on historical events. This adds valuable context about the data lifecycle and aligns perfectly with the destructiveHint=false annotation.

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 action, and every sentence adds value: the first covers the core operation and constraint, the second explains data behavior. No unnecessary 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?

The description covers the action, ownership constraint, and soft-delete behavior, which is sufficient for a simple tool. It omits return-value details, but since there is no output schema and the operation is straightforward, this is a minor gap rather than a major deficiency.

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 fully describes the single 'id' parameter with high coverage, and the tool description does not add meaningful detail beyond the schema. Baseline 3 is appropriate given the schema does the heavy lifting.

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 a specific verb and resource: 'Cancel a subscription by id.' It clearly distinguishes this from siblings like subscribe and list_subscriptions, and the ownership constraint adds clarifying detail about the scope.

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 usage context: you can only cancel your own subscriptions, and it references recent_alerts for historical consequences. It does not explicitly name alternative tools or when-not-to-use scenarios, but the ownership limitation serves as a key constraint.

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