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

Annotations already cover readOnly/idempotent/non-destructive, but the description adds real context beyond them: an owner-only authorization requirement, that the call reports live provider MX state rather than stored proof, and the operational caveat to keep existing business-mail MX records. It does not discuss rate limits or response shape, which keeps it short of a 5.

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?

Five short clauses, front-loaded with the core purpose, each carrying a distinct fact (auth scope, required params, return semantics, MX caution, guide pointer). Slightly telegraphic, and the MX-warning sentence sits apart from the flow, but there is 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 and a nearly opaque payload, the description still supplies the required input meaning, the authorization model, what is reported back, and a pointer to the workflow guide resource. Adequate for a read-only inspection tool; a little more on the returned MX-state shape would complete it.

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 schema's payload is a bare additionalProperties object with no per-field documentation, so the description carries the burden and does so: it names domainId as required and replyDomainId as optional with meaning ('already connected child subdomain'). It does not clarify the payload fields the schema alludes to generically (expectedRevision, cursor, reviewHash).

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+resource pair ('inspect' + 'owner-only reply setup inspection'), and 'email reply domain' is clearly distinct from the write sibling configure_email_reply_domain. It does not explicitly name that sibling, so an agent must infer the inspect/configure split from the surrounding tool list rather than from the text.

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 clear operational context: owner-only, requires domainId for the sending domain, replyDomainId only for an already-connected child subdomain. It also implicitly scopes usage by noting 'read alone does not activate or refresh stored sending proof', steering the agent away from expecting this call to mutate anything, though it never names the alternative tool to use for activation.

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