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

Adds useful context beyond annotations: it performs an external DNS lookup (consistent with openWorldHint) and returns records the user must add. However, 'Check' reads as read-only while readOnlyHint=false implies it may persist state/status; the description does not clarify that the mailbox status is written, and says nothing about failure cases or propagation delay.

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 with no filler: the purpose leads and the return shape follows. Nothing is repeated from the title and every sentence carries information.

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?

There is no output schema, and the description only partially covers returns ('the mailbox with the domain's status and the records to add') without indicating status values, record format, or what happens on lookup failure. Adequate for a one-parameter tool, but leaves real gaps an agent would hit when interpreting results.

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 single mailboxId parameter is fully documented (including its source from add_support_email or get_setup_status). The description adds no further meaning about the parameter, 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 ('Check the DNS records') and resource (a mailbox's domain / sending domain), and clarifies the goal is enabling replies to be sent from the mailbox's own domain. It is distinguishable from nearby tools like send_forwarding_test or get_setup_status, though it never names those alternatives directly.

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?

Usage is only implied: 'the records to add' suggests this belongs to the email setup flow, but there is no explicit when-to-call guidance, no prerequisites (e.g. call after add_support_email), and no mention of alternatives or how often to re-check.

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