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

The annotations already declare destructiveHint=true, so the description doesn't need to emphasize destructiveness. The description adds minimal behavioral context beyond this, such as clarifying that it applies to 'active' sends, but doesn't disclose side effects like whether the cancellation is reversible or what happens to associated resources.

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 clear sentence with no unnecessary words or redundancy. It is highly 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 the tool's simplicity, the description adequately covers the basic operation. However, it lacks explicit mention of prerequisites (e.g., needing an active send) and does not reference sibling tools for comparison. An output schema exists but is not shown; still, the description is largely sufficient for a straightforward cancel action.

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?

Both parameters have full schema descriptions (100% coverage), so the description adds no additional meaning beyond what the schema provides. The baseline 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 clearly states the verb 'cancel' and the resource 'active PromptFax send', making the tool's purpose unambiguous. It effectively distinguishes from sibling tools like 'send_fax' or 'retry_failed_fax'.

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 mentions when to use it (for canceling an active send) but provides no explicit exclusions, prerequisites, or alternatives among sibling tools. Usage context is implied rather than explicit.

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