Currently active registrar promo/coupon codes, biggest discount first.
| Name | Required | Description | Default |
|---|---|---|---|
| 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?
With no annotations, the description carries the full burden: it does disclose a filter (only currently active codes) and a sort order (discount descending), which is genuine behavioral value. However, it says nothing about authentication needs, result size/pagination relative to the limit param, or what the returned code data looks like.
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 fragment with no filler; the scope and ordering are stated immediately. Slightly terse for the amount of unexplained behavior it leaves, but nothing is wasted.
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 simple two-param list tool with no output schema or annotations, the description covers scope and ordering but leaves return shape, auth requirement, and the meaning of limit unstated. Adequate but with clear gaps.
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 only 50%: api_key is documented in the schema, but limit has no description at all and the description does not explain it (default 25, max 100). The 'biggest discount first' ordering hints at relevance but does not clarify what limit caps or how to page.
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 resource (registrar promo/coupon codes) and bounds it ('currently active') with an explicit ordering ('biggest discount first'). It is distinguishable from siblings like list_registrars and get_tld_prices, though it omits an explicit verb like 'list'.
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?
There is no statement of when to use this tool versus alternatives (e.g., get_tld_prices, list_registrars, compare_tlds), which is the natural place a coupon lookup would compete with a plain price lookup. Usage must be inferred entirely from the name and resource.
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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