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

Beyond the annotations (readOnly=false, destructive=false, idempotent=true), the description adds valuable context: ownership enforcement, deactivation instead of deletion, and that historical events remain accessible via recent_alerts. This fully discloses side effects and aligns with annotations.

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, each packing meaningful information. The first states the core action, the second clarifies ownership and side effects. 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?

Given the tool's simplicity (one parameter, no output schema), the description covers purpose, ownership constraint, side effect, and the relationship to recent_alerts. This is sufficiently complete for an agent to select and invoke the tool correctly.

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 sole parameter id as 'Subscription id (uuid) returned by subscribe.' The description adds no new parameter-level detail beyond restating 'by id', so baseline 3 is appropriate.

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.' It uses a specific verb and resource, and differentiates from siblings by explaining that the row is deactivated rather than deleted, so historical events remain available.

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 implies when to use the tool (to cancel a subscription) and provides a prerequisite (the id returned by subscribe). It does not explicitly name alternatives or exclusions, but the sibling list and phrase 'by id' give sufficient context.

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