List domain extensions (TLDs) with the cheapest registrar for first-year registration, renewal, transfer and 3-year total. Prices in USD/year.
| Name | Required | Description | Default |
|---|---|---|---|
| q | No | Only TLDs containing this text, e.g. "ai" | |
| sort | No | popularity | |
| type | No | gtld or cctld | |
| limit | No | ||
| 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?
No annotations are provided, so the description carries the full burden. It discloses the return content and currency ('Prices in USD/year') and 'List' implies a read-only operation, but it omits rate limits, auth requirements, and side-effect profile.
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 concise sentences, front-loaded with the core purpose and return fields. Every phrase earns its place; 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 tool with no annotations and no output schema, the description partially covers return values. However, it leaves meaningful gaps around sibling differentiation, usage context, and parameter behavior that an agent would need for reliable invocation.
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 60%, leaving sort and limit undocumented in structured fields. The description adds no parameter-level meaning, such as how filtering, sorting, or limiting interacts with the cheapest-registrar results.
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 ('List') and resource (domain extensions/TLDs) with what the list contains: cheapest registrar for first-year registration, renewal, transfer, and 3-year total. The purpose is clear, but it does not explicitly differentiate from siblings like compare_tlds or get_tld_prices.
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 mentioned. The description implies the tool is for finding cheapest TLDs, but it does not say when to choose it over compare_tlds, get_tld_prices, or other siblings.
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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