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

The description adds substantial behavior beyond the annotations: the cancellation is deferred to the end of the Stripe period, paid watches are closed but remain readable for 30 days, and the free watch plus agent tokens are unaffected. It also discloses the not_paid and token_required error paths and the bearer-token auth requirement, which is exactly the kind of operational context annotations cannot express.

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 front-loaded with the core effect and timeline, then moves to side effects, preconditions, and auth. It is mostly efficient, though 'Contract 0.4.0' is a slightly unexplained detail that may not help an agent decide whether to call the tool.

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 a zero-parameter but destructive plan-cancellation tool with an output schema already available, the description is complete enough to call correctly. It covers the deferred timing, affected resources, preserved resources, auth requirement, business precondition, and two error outcomes.

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?

This tool has zero input parameters, so there are no parameter semantics to explain; the baseline for 0 params is 4. The description appropriately focuses on preconditions and side effects instead of inventing parameter details.

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 states a specific verb and resource: it 'stops the paid plan at the end of the Stripe period' and explains what happens to paid watches. It is clear on its own, but it does not distinguish itself from the sibling cancel_creator_plan, so an agent must infer which plan each tool applies to.

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?

It gives an important precondition/branch: 'Without a paid plan the tool answers not_paid,' and it states the required organisation token. However, it never says when to choose cancel_plan instead of cancel_creator_plan or any other sibling, leaving the main routing decision implicit.

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