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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds genuine context by saying the response includes verification state and DNS record statuses, which is useful since no output schema exists. It still omits whether the data is cached or freshly checked, which matters given the check_* siblings.

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?

A single front-loaded sentence with no filler; the identifier and the payload are both stated in one clause and nothing is repeated.

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 one-parameter read tool this covers purpose and return contents adequately, but the missing parameter format and the lack of differentiation from check_sending_domain leave real gaps for an agent choosing and calling 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?

Schema coverage is 0% for the single parameter, so the description must carry the meaning of sending_domain_id and does not – an agent cannot tell whether it expects a UUID, a numeric ID, or the bare domain name. This is a meaningful ambiguity for the only required input.

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 names a specific verb and resource ("Read one sending domain") and even previews the returned facts (verification state, per-record DNS status). It does not, however, distinguish itself from the sibling check_sending_domain, which sounds like an overlapping operation, so it falls short of a 5.

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?

"Read one" implies a single-item lookup versus list_sending_domains, but there is no explicit statement of when to use this instead of check_sending_domain or list_sending_domains, and no prerequisites or exclusions are given.

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