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

The description adds meaningful behavioral details beyond the annotations: the row is deactivated rather than deleted, and historical events remain accessible via recent_alerts. This clarifies the non-destructive nature explicitly (matching destructiveHint=false) and explains the post-condition in a way the annotations alone do not.

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 exactly two sentences, with the primary action front-loaded. The second sentence packs essential constraints and side effects into a compact, clear structure, and every phrase contributes to understanding the tool's behavior.

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 cancellation tool, this description is complete: it states the action, ownership requirements, and the non-destructive outcome. Since there is no output schema, the description carefully covers the tool's side effects and relationship to recent_alerts, giving an agent everything needed to invoke it 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?

With only one parameter and 100% schema description coverage, the schema already fully documents the parameter ('Subscription id (uuid) returned by subscribe'). The description only repeats 'by id' without adding new semantic detail, so it stays at the baseline for good schema coverage.

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 opens with 'Cancel a subscription by id,' a specific verb+resource pairing that clearly identifies the tool's action and scope. It distinguishes itself from related tools like subscribe and list_subscriptions by focusing on cancellation, and it references recent_alerts to clarify the relationship between deactivation and historical data.

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 by stating ownership is enforced—only the user's own subscriptions can be canceled—which is a critical constraint for invoking the tool. It doesn't explicitly name alternative tools or include 'when not to use' guidance, but the purpose is unambiguous enough to infer appropriate usage.

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