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

Beyond annotations (mutation, not destructive), description adds that the row is deactivated rather than deleted, keeping historical events available via recent_alerts, and enforces ownership.

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 focused sentences: first states purpose, second adds behavioral detail. No fluff, front-loaded, every sentence earns its place.

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?

Covers cancellation, ownership, side effects (deactivation), and link to recent_alerts. Lacks output description but tool is simple; adequately complete given complexity.

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?

Schema already documents the single 'id' parameter with description (uuid from subscribe). Description adds ownership context but no additional parameter detail beyond 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?

Description states 'Cancel a subscription by id' with a specific verb and resource, and distinguishes from siblings like 'subscribe' (create) 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?

Clearly states ownership enforcement ('only cancel your own subscriptions'), providing correct usage context, but does not explicitly mention when not to use or alternatives.

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