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

readOnlyHint=true already tells the agent this is a safe, non-mutating call. The description goes further by disclosing the return payload ({ domain, available, premium }) — valuable since no output schema exists — and by giving the underlying API route. It stops short of noting rate limits or what 'premium' implies (e.g., premium pricing tier).

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 compact sentences, with the core purpose front-loaded and the return shape plus API endpoint following. Every element earns its place with 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?

For a single-parameter read tool with no output schema, the description covers purpose, return fields, and endpoint, which is nearly everything an agent needs. Minor omissions (premium field meaning, error behavior for invalid or registered domains) keep it from being fully exhaustive.

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 'domain' parameter is documented in the schema with a format example, so the schema carries the parameter burden. The description adds no extra semantics beyond the parameter name itself, making the baseline of 3 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?

The description states a specific verb and resource (check a domain's availability to register), which cleanly separates it from retrieval siblings like dnsimple_get_domain and dnsimple_list_domains. It does not name any sibling explicitly, but the 'available to register' scope is unambiguous enough that an agent can route correctly.

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: an agent can infer this is a pre-registration lookup. There is no explicit statement of when to call it versus dnsimple_get_domain or dnsimple_get_domain_prices, nor any note about prerequisites such as the account/domain being reachable.

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