Fetch a URL and return an AI summary with key points. $0.02 USDC via x402.
Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"url": "<url>"
},
"name": "summarize_url"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | ||
| length | No |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full disclosure burden, and it does add one genuinely useful behavioral fact: the call costs $0.02 USDC via x402, implying a payment flow the agent must be prepared for. However, it says nothing about failure modes, paywalled or JavaScript-heavy pages, timeouts, rate limits, or whether the fetch result is cached, all of which matter for a network-bound paid tool.
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 short sentences with zero filler, and the core action plus the cost caveat are both front-loaded. Nothing needs trimming and nothing is buried.
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 and no annotations, so the description must stand alone; it conveys the return shape at a high level ('AI summary with key points') and the payment requirement. It falls short on the undocumented 'length' option and on any indication of what happens when the fetch fails or the content cannot be summarized.
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 0% for two parameters, so the description needed to compensate and does not: the 'length' enum (short/long) is never mentioned, and its effect on the summary is undefined. Only 'url' is implied by the phrase 'Fetch a URL', which an agent could infer from the parameter name alone.
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+resource pair ('Fetch a URL and return an AI summary with key points'), which is far more informative than the bare name. It does not explicitly distinguish itself from the sibling extract_url, so an agent must infer that this one summarizes rather than extracts raw content.
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 or when-not-to-use guidance is given, and the closest sibling (extract_url) is never mentioned, leaving the agent to guess which of the two to pick. The only contextual cue offered is the price, which helps decide whether to spend money but not which tool to call.
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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