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

Annotations already provide idempotentHint and destructiveHint, and the description adds the key context that the broadcast itself is preserved, which refines what 'destructive' means here. It does not overpromise or contradict the annotations.

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 short sentences with no filler. The primary action is front-loaded, and the clarifying scope ('broadcast itself is kept') earns its place immediately.

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 single-parameter, no-output-schema tool, the description plus annotations cover the essential behavior: what is canceled, what is preserved, and that the operation is destructive-but-idempotent. Minor missing context about response values or no-op behavior is acceptable given the tool's simplicity.

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 coverage is 100%: the only parameter, broadcast_id, is already described as 'The broadcast id'. The description adds no new parameter-level detail beyond tying it to the broadcast being canceled, so baseline 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 states a specific verb ('Cancel') and a precise resource ('a broadcast's scheduled send'), and clarifies the broadcast itself is kept, distinguishing this from delete_broadcast and other cancellation tools. This is unambiguous and actionable.

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 for future scheduled sends rather than sent messages, but it does not explicitly state when to prefer this over siblings like cancel_message, cancel_automation, or delete_broadcast. No alternatives or exclusions are named.

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