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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered without prose. The description adds the non-obvious authorization requirement (`full_access` API key) and the canonical endpoint/operationId, which is real context beyond the structured fields. It omits behavior when the id does not exist (e.g., a 404), keeping it out of the top band.

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 short sentences, the identity of the operation first and the prerequisite second. No filler, no restatement of the title beyond what is needed.

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 with complete annotations, the description covers the call mechanics and auth. However, there is no output schema and the description never says what a domain record contains or how failures are signaled, so the return contract is undocumented anywhere in the definition.

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%, so the schema alone only says `id: string (uuid)` with no meaning attached. The description partially compensates by showing the path template `GET /domains/{id}`, making clear the id identifies a domain, but adds no format hints, sourcing guidance, or note on whether the id is the domain's UUID or a name.

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 gives a specific verb+resource ("Retrieve a domain") and pins it to the exact endpoint `GET /domains/{id}` (operationId `getDomain`), which unambiguously separates it from list_domains or get_audience. It never explicitly names a sibling to contrast with, so it stops 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?

There is no statement of when to use this versus list_domains, get_domain's update/delete/verify siblings, or how the caller should already know the id. The only conditional content is an API-key prerequisite, which is a gating requirement rather than usage guidance.

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