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

Annotations only declare the generic profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false, openWorldHint=true); the description adds the concrete behavior those hints cannot convey: DNS is checked against an external system, routing is activated conditionally on success, the attempt is recorded, and status plus next steps are returned.

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?

Three tight sentences, front-loaded with the action and its condition, followed by side effects and the sibling alternative. No filler and nothing duplicated.

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-param mutation tool with no output schema, the description covers the precondition, the mutation performed, the side effect (recorded attempt), and the shape of the response (status and next steps). An agent has everything needed to call it 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?

Schema coverage is 100% and the schema already documents both params ('Target app id', 'Existing hostname to verify and activate'). The description's 'already attached' wording largely restates the domain param rather than adding format or constraint detail, so the baseline 3 applies.

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?

States specific verbs and resource: checks DNS for a hostname already attached, and activates routing on success. It explicitly differentiates itself from the read-only sibling get_custom_domain_instructions, so an agent can pick between them without opening either schema.

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?

Gives a precondition ('hostname already attached to this app') and an explicit alternative with its selecting condition ('use get_custom_domain_instructions for a read-only status check'). Both when-to-use and when-not-to-use are covered.

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