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

Annotations already declare readOnlyHint=true, and 'Retrieve' is consistent with that, so there is no contradiction. The description adds the REST endpoint path, which is mildly useful context, but says nothing about what happens on a nonexistent domain (404), authentication needs, or rate limits.

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 with the primary action front-loaded and no filler. Every clause carries information and nothing is buried.

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 trivial single-resource GET with one fully documented parameter and a readOnly annotation, the essentials are present. With no output schema, the description also does not hint at the returned domain object's contents, so the agent knows how to call it but not what to expect back.

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?

There is only one parameter and schema description coverage is 100%, with the schema itself supplying the 'example.com or numeric id' example. The description's 'by name or id' merely restates that, adding no format, validation, or lookup-failure semantics, so baseline 3 is appropriate.

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 ('Retrieve a single domain by name or id'), which is clearer than a bare name restatement and signals lookup of one item versus a collection. It does not, however, explicitly differentiate itself from siblings like dnsimple_list_domains or dnsimple_check_domain, leaving that inference to the agent.

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 implied by 'single domain' but there is no explicit when-to-use or when-not-to-use guidance, and no routing to alternatives such as dnsimple_list_domains for enumeration or dnsimple_check_domain for availability checks. Adequate but leaves the agent to infer the selection logic.

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