Check whether an x402 endpoint is alive and emits a valid HTTP 402 payment challenge, before you pay it. Free liveness check. Returns reachability, status code and whether a valid challenge was found.
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | Absolute https URL of the x402 resource to check. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden of behavioral disclosure. It states the operation is free, describes what it returns ('reachability, status code and whether a valid challenge was found'), and implies a network request to the endpoint. It does not detail potential side effects, but as a read-only liveness check, this is adequately transparent.
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?
The description is three concise sentences with no filler. The primary purpose is front-loaded, followed by the key attribute 'Free liveness check', and finally the return values. Every sentence contributes necessary information.
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 single-parameter tool with no output schema, the description is complete: it explains what the tool does, when to use it, that it is free, and what it returns. An agent can correctly invoke this tool without needing additional details about expected inputs or outputs.
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?
The schema already provides 100% coverage for the single parameter, describing 'url' as 'Absolute https URL of the x402 resource to check.' The tool description adds only the synonym 'x402 endpoint' and does not introduce additional semantics such as formatting nuances or edge-case behavior. Baseline 3 is appropriate.
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 clearly states the verb 'Check', the resource 'x402 endpoint', and the specific condition being verified: 'alive and emits a valid HTTP 402 payment challenge'. This distinguishes it from sibling tools like x402_audit_merchant or x402_market_stats, which address different concerns.
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 'before you pay it' provides a clear when-to-use context, indicating this tool is a preliminary verification step prior to payment. It also notes the check is free, which signals a low-cost pre-payment action. However, it does not explicitly mention alternatives or when not to use the tool, though sibling tools serve clearly different purposes.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Each tool targets a distinct aspect of the x402 ecosystem: endpoint liveness, deep merchant audit, facilitator comparison, gas pricing, market analytics, and verified merchant listings. There is no real overlap between tools.
All tools share the x402_ prefix and snake_case, but only audit_merchant and check_endpoint follow a verb_noun pattern. The remaining tools are noun phrases like gas_price, market_stats, and verified_merchants, making the naming conventions mixed yet still readable.
Six tools is well-scoped for an ecosystem intelligence server. Each tool fills a distinct niche and none feel redundant or superfluous.
The tool set covers the entire discovery and research workflow for the x402 economy: checking endpoints, finding verified merchants, auditing merchant trustworthiness, choosing facilitators, estimating gas costs, and assessing market viability. No obvious dead ends or critical gaps.