Every registrar’s current register / renew / transfer price for one extension (e.g. "com", "io", "co.in"), cheapest first, plus average and median.
| Name | Required | Description | Default |
|---|---|---|---|
| tld | 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?
With no annotations, the description carries the full burden. It usefully discloses the return shape (ordered cheapest-first plus average/median), which is real behavioral information, but says nothing about data freshness, rate limits, or auth expectations beyond what the schema already documents for api_key.
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 that front-loads the core resource and ends with the aggregation detail. No waste, though the parenthetical examples and aggregate clause make it slightly crowded.
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?
No output schema exists, so the description's explanation of return values (cheapest first, average, median) is the right thing to include and it does. For a simple two-parameter read tool, the remaining gap is only around data recency and auth fallback, both minor.
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%: api_key is documented in-schema but the required tld parameter has no schema description. The description partially compensates by giving concrete examples ('com', 'io', 'co.in'), clarifying the expected format, but adds no syntax constraints (no leading dot, casing).
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 (registrar prices for one TLD) and defines the scope precisely: one extension, cheapest first, with average and median aggregates. This contrasts implicitly with the multi-TLD siblings (compare_tlds, find_cheapest_tlds), though it never names them.
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 phrase 'for one extension' implies the usage condition (single-TLD lookups) versus multi-TLD tools, but there is no explicit when-to-use, when-not, or named alternative. Guidance is inferable rather than stated.
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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