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

The description discloses meaningful behavioral details beyond the annotations: the cancellation may result in a refund, a free pass, or being counted, and it requires stating the rule before a late cancellation. This helps the agent anticipate consequences and follow a required step, even though annotations already indicate this is not read-only or idempotent.

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 two sentences with no filler. It front-loads the action and immediately adds the most important behavioral condition and the required pre-cancellation communication step. 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?

For a two-parameter cancellation tool with no output schema, the description provides enough context about what the outcome will communicate and the rule-related behavior. It could be more complete by describing the exact output structure, but the essential invocation and consequence information is present.

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 input schema already documents both parameters with 100% coverage: lessonId is 'The lesson id from book_lesson' and token is 'The student's personal token.' The description adds no additional parameter-level meaning, so the baseline score of 3 is appropriate.

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 uses a specific verb and resource: 'Cancel a student's lesson' and clarifies the cancellation happens 'under the coach's rules.' It also tells what the outcome communicates, which distinguishes it clearly from booking-related siblings like book_lesson.

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 clearly implies when to use the tool: to cancel a student's lesson. It also provides useful context by explaining that the outcome depends on coach rules and adds a specific procedural requirement for late cancellations: 'Say the rule to the person before cancelling late.' It does not explicitly name alternatives, but the usage context is clear.

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