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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds useful context beyond that: it discloses the evidence sources (registry RDAP plus independent evidence) and that premium quotes are kept separate from standard TLD pricing, but it says nothing about latency, rate limits, or result shape.

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 sentences, front-loaded with the core action, and no filler. The premium-vs-standard caveat is slightly awkwardly phrased but earns its place by warning about a real misread of results.

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?

With no output schema, the description correctly outlines what the tool returns conceptually (availability verdict plus a price comparison). For a one-parameter read-only tool with full annotation coverage, it is nearly sufficient; a note on domain format or on when to prefer compare_registrar_prices would close the remaining gap.

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 description coverage is 0% and the single 'domain' parameter is undocumented in the schema, so the description is the only source. It implies a single domain string but never states format or whether subdomains/URLs are accepted, so baseline 3 for a self-evident one-parameter tool with a small gap.

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 (check), resource (domain availability + registrar prices), and mechanism (registry RDAP plus independent evidence). The qualifier 'one domain' signals single-domain scope, though it does not name or contrast any of the siblings (compare_registrar_prices, calculate_domain_cost).

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 'Check one domain' – it is the single-domain lookup, as opposed to the sibling comparison tools. However, there is no explicit when-to-use/when-not statement and no sibling is named as an alternative, so the agent must infer routing.

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