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

The description adds context beyond the annotations by specifying that cancellation occurs at the end of the billing period, not immediately. This aligns with the non-destructive hint and idempotent hint, providing useful behavioral transparency.

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 a single sentence with no wasted words, clearly communicating the action and timing. It is appropriately concise and front-loaded.

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 no parameters and the existence of an output schema, the description explains the core action and timing. It could mention the post-cancellation state (e.g., downgrade to free), but overall it is fairly complete for a simple tool.

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?

There are no parameters, and schema coverage is 100%, so the description does not need to add parameter information. The baseline for no parameters is 4.

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 tool cancels a Pro subscription at the end of the current billing period, which is a specific verb+resource combination and distinguishes it from siblings like upgrade_to_pro and create_billing_portal_session.

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 the tool should be used when the user wants to cancel their Pro subscription at period end, but it does not explicitly state when not to use it or provide alternative tools for other cancellation scenarios (e.g., immediate cancellation).

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