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

The description says cancellation requires accepting data removal and that 'what the plan added ends,' which conflicts with the annotation destructiveHint=false. This is a material contradiction for a cancellation operation that explicitly accepts loss of plan-added data.

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 key cancellation behavior is front-loaded and useful, but the description becomes lengthy and includes usage-unit pricing details that are not clearly necessary for invoking cancel_plan. Some sentences about page/report/alert/tender-watch units feel tangential to the cancellation action.

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 complex cancellation tool with no output schema, the description covers important effects: stopping charges, keeping paid periods active, refund timing for recent or unstarted purchases, and exceptions for USDC/credit payments. It still does not describe the immediate response shape, but it provides substantial business context beyond the schema.

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 is one required boolean parameter with 100% schema description coverage, so the schema already explains that it must be true and means accepting loss of plan benefits. The description reinforces this but adds no additional syntax or parameter-specific constraints beyond the 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?

The description opens with a specific verb and resource: 'Cancels the active plan.' It immediately clarifies scope and consequences, making it clearly distinct from sibling tools such as buy_plan, list_plans, and billing.

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 this is the cancellation action and gives some conditional behavior, including that USDC or credit purchases require an e-mail refund request. However, it does not explicitly state when to use cancel_plan versus related siblings like buy_plan, list_plans, or billing.

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