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

Annotations already declare destructiveHint=true, so the primary behavioral trait is known. The description adds value by specifying that the confirm parameter must be set to 'DELETE', a safety requirement not captured by annotations. This adequately discloses the mandatory confirmation step, though it omits details on irreversibility or side effects.

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, front-loaded with the purpose, and includes a critical usage condition. Every word earns its place without redundancy or fluff.

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 simple destructive tool with annotations and no output schema, the description covers the essential purpose and a key parameter constraint. It lacks details on the nature of the 'customDomainId' or any return behavior, but overall it provides sufficient context for an agent to use the tool correctly.

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 has 2 parameters with 0% description coverage, so the description must compensate. It partially explains the 'confirm' parameter by requiring it to be 'DELETE', but it provides no meaning for the required 'customDomainId' parameter, leaving the agent unsure of what ID to provide.

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 'Delete an external custom domain owned by the authenticated user,' which is a specific verb-resource combination. It distinguishes this tool from sibling tools like 'disconnect_custom_domain' and 'delete_business_custom_domain' by focusing on the user's own external custom domain.

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 provides a key requirement: 'Requires confirm set to DELETE,' which guides the agent on the mandatory value for the confirm parameter. However, it does not explain when to use this tool versus alternatives like 'disconnect_custom_domain' or 'delete_business_custom_domain', leaving the agent to infer context from the tool name alone.

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