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

Beyond the annotations (readOnly, idempotent, openWorld, non-destructive), the description discloses live WHOIS lookups, a 5-minute result cache, and a rate limit of 120 checks per 10 minutes, plus the conditional behavior of returning a transfer link when the domain is taken. These are exactly the operational traits annotations cannot express.

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 dense sentence leads with the availability answer and folds freshness, rate limits and outputs into compact parentheticals. No filler or repetition of the title.

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 carries the return-value burden and does so: registrability, one-year register/transfer/renewal prices for the extension, and the order or transfer link. Combined with 100% schema coverage for the three parameters, an agent has everything needed to call and interpret 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 description coverage is 100%, so lang, domain and currency are already well documented in the schema. The description only adds 'one name per call' for the domain parameter and says nothing about lang or currency semantics, so baseline 3 applies.

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: checking whether a domain can be registered at Ex2, plus the side outputs (prices, order/transfer link). It is distinguishable from siblings like get_domain_pricing because it centers on live WHOIS availability, though it never names an alternative explicitly.

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 (check availability before ordering) and the practical constraint 'one name per call; limited to 120 checks per 10 minutes' is given. However, there is no explicit guidance on when to prefer this over get_domain_pricing or the plan-comparison siblings.

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