List valid BuiltWith MCP registry category slugs, labels, and entry counts (v2). This public endpoint requires no API key and uses no API credits.
This tool declares no required parameters. Add optional parameters from the input schema as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {},
"name": "mcp-list-categories"
}
}| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description adds meaningful context beyond the annotations: it is a public endpoint, requires no API key, and consumes no API credits — exactly the operational facts an agent needs before calling. It does not describe error behavior or result size, but for a zero-parameter catalog read that is a minor omission. Note the annotations' readOnlyHint=false is inconsistent with a listing tool, but the description does not itself assert a write, so this is not a description-level contradiction.
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 sentences, no waste, with the core purpose and returned fields front-loaded and the access/cost constraints following. The trailing '(v2)' is the only slightly under-explained token.
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's enumeration of return fields does real work, and the auth/cost statement covers the main operational question. The unexplained 'v2' and the absence of any note on response shape or size keep it from being fully complete for a discovery endpoint.
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?
With zero parameters, the baseline is 4; there is nothing to disambiguate. The description does use the space well by enumerating the returned fields (slugs, labels, entry counts), which is the closest thing to parameter-relevant semantics for a no-argument tool.
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 opens with a specific verb and resource ('List valid BuiltWith MCP registry category slugs, labels, and entry counts') and even names the exact fields returned. It is clearly distinguishable from generic siblings like list-api or mcp-list-api, though it never explicitly contrasts itself with 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?
Usage is only implied: an agent can infer this is the discovery step for obtaining valid category slugs before calling a category-based tool. There is no explicit when-to-use statement, no when-not-to-use, and no named alternative (e.g., whether mcp-list-api covers this).
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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