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

Annotations already declare readOnlyHint=false and destructiveHint=false, and the description adds valuable context: ownership is enforced, and the row is deactivated rather than deleted, so historical events remain accessible via recent_alerts. This explains side effects beyond what annotations convey and aligns with the destructiveHint flag. No contradiction 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 sentences with no wasted words; the purpose is front-loaded and each clause contributes either the action, a constraint, or the side effect. This is exemplary conciseness.

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 single-parameter mutation tool with annotations covering safety, the description covers the action, ownership, and post-effect (soft delete). It even points to recent_alerts for historical data. It could hint at return behavior, but given the simplicity and existing annotations, it's sufficiently 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 schema already provides 100% coverage for the id parameter with its description. The description adds a meaningful constraint by stating ownership is enforced, clarifying that only ids belonging to the caller are valid. This goes beyond the schema's basic uuid description.

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 that clearly states the action. It distinguishes itself from siblings like subscribe and list_subscriptions by focusing on cancellation. The ownership enforcement adds further clarity on 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 implies use when you want to cancel a subscription, with the explicit constraint that you can only cancel your own. It references recent_alerts for post-cancellation history, but does not explicitly contrast with sibling tools like list_subscriptions or subscribe. The ownership requirement serves as a clear precondition, though alternatives are not named.

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