Compare registrar prices across up to 20 extensions side by side.
| Name | Required | Description | Default |
|---|---|---|---|
| tlds | 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?
No annotations exist, so the description carries the full behavioral burden, and it discloses almost nothing beyond the operation itself. It does not state that this is a read-only lookup, that results come from live registrar queries, whether calls are rate limited, or what the comparison response contains. The only behavioral detail (the 20-extension cap) is duplicated from the schema.
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 front-loaded sentence with no filler; the action and scope come first. It is efficient, though its brevity leaves gaps rather than being maximally economical.
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 annotations, no output schema, and only 50% parameter coverage, the description should explain the read-only nature and what the comparison returns. It does neither, leaving an agent unable to interpret results or confirm the tool's side-effect profile.
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?
Only the api_key parameter is documented, and that documentation lives in the schema, not the description. The description restates the tlds array's maxItems=20 rather than clarifying the required string format (with or without a leading dot, case sensitivity) or whether multiple extensions are compared against one domain or several. It adds essentially no meaning over the structured fields.
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?
Specific verb (compare) plus resource (registrar prices) and scope (across extensions side by side), which separates it from find_cheapest_tlds and get_tld_prices. It never names those siblings explicitly, so differentiation is inferential rather than stated.
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: pick this when you want a side-by-side view of several extensions. There is no explicit statement of when to prefer it over find_cheapest_tlds (single cheapest) or get_tld_prices, and no mention of prerequisites or exclusions.
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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