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

Annotations already declare the mutation/idempotency/open-world profile, and the description adds meaningful state context beyond them: the domain serves no traffic and gets no certificate until verification. It does not mention that repeated calls are safe (idempotentHint) or permission requirements, but the added lifecycle detail is substantive.

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?

Two tight sentences, front-loaded with the action and its return value, then the consequence of not verifying. No filler.

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?

With no output schema, the description usefully discloses the return value (the DNS TXT record) and the inactive-until-verified state. It leaves only minor gaps, such as what happens on a duplicate connect, for a two-parameter tool.

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 description coverage is 100% and both parameters are well documented in the schema (hostname format, ownership requirement). The description adds no parameter-level 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 a specific verb and resource ('Attach a custom domain ... to an agent') and goes further by naming the return value (DNS TXT record). An agent can distinguish this from siblings like verify_domain, remove_domain, and list_domains without opening a 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?

The description makes the workflow context clear: the domain stays inactive until the TXT record is verified, which implies the follow-up verify_domain step. It does not explicitly name verify_domain or state when not to call this (e.g., for an already-connected domain), so it falls short of full routing guidance.

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