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

Annotations already declare readOnly, openWorld, non-destructive and non-idempotent, so the description's added value is in the operational details it supplies: a live external registry call, a 10-checks-per-minute throttle, and the broker link returned for taken domains. These are real behavioral disclosures an agent cannot get from the annotations. What's missing is what happens on an invalid or malformed name and whether partial results are possible, but the added context is above baseline.

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 verb and scope, followed by the return payload and the rate limit. No filler, no restatement of the title, and every clause carries information the agent needs.

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 shouldered the burden of describing returns and does so field-by-field (availability, first-year/renewal/transfer price, cart link, broker link). The rate limit and the external-registry nature round out what a two-parameter, annotation-covered tool needs.

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%, so both `domain` and `currency` are already documented including the ISO 4217 pattern and the unsupported-code error behavior. The description's example ('mybrand.com, mybrand.ae') marginally extends the schema by signalling non-.com TLD support, but it adds no syntax or constraint detail beyond the schema, so the baseline of 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 names a specific verb and resource — 'live registry check of one domain name' — and enumerates exactly what the response contains (availability, first-year price, renewal, transfer, cart link, broker link if taken). The 'one domain name' scope and registry origin make it unmistakably different from the catalog/search siblings.

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?

The when-to-use context is implied by 'live registry check' for a single name, and the fallback path is stated ('if taken, returns a link to the domain broker service'). However, there is no explicit statement of when to call this versus alternatives such as search_products or build_cart_link, and no exclusions or prerequisites (e.g. that the name must be user-supplied, not guessed).

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