check_domain_availabilityLive availability check for a full domain name (RDAP, WHOIS fallback). available is null if the registry could not be reached.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | ||
| api_key | No | Your TLDers API key. Only needed if your client cannot send an Authorization header or use a ?key= URL. |
Changes observed during successful MCP inspections.
Input schema / properties / api_keyAdded value: +{
+ "description": "Your TLDers API key. Only needed if your client cannot send an Authorization header or use a ?key= URL.",
+ "type": "string"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld). The description adds genuine value beyond them by disclosing the lookup mechanism (RDAP with WHOIS fallback) and the failure semantics — that 'available' is null when the registry is unreachable — which an agent needs to interpret the result.
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, front-loaded with the core purpose and then the return-value caveat. Every clause earns its place with zero 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?
There is no output schema, so the description wisely covers the critical return field ('available' is null on registry failure). For a two-parameter read-only tool this is largely complete, though it omits what a successful result otherwise contains.
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 50%: the api_key parameter is documented in the schema, but 'domain' is bare. The description partially compensates by clarifying that a 'full domain name' (not just a TLD) is expected, but adds no format or validation detail.
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 ('Live availability check for a full domain name') and names the underlying mechanism (RDAP, WHOIS fallback). It is clearly distinct from the pricing-oriented siblings, though it does not explicitly differentiate itself from them in text.
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?
No when-to-use guidance or alternatives are given. The phrase 'full domain name' implies an input prerequisite, but there is no statement about when this tool should be chosen over siblings like get_tld_prices or compare_tlds.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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