xportalx

x402_proxy

Access x402-protected APIs with automatic payment. Dynamic pricing: 0.01 USDC fee + target cost. Supports USDC on Base.

Tool call template

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": {
      "targetUrl": "<targetUrl>"
    },
    "name": "x402_proxy"
  }
}

Input Schema

Name	Required	Description	Default
`targetUrl`	Yes	The x402-protected URL to access
`targetBody`	No	Request body for POST/PUT requests
`paymentProof`	No	Transaction hash of USDC payment (required after initial 402 response)
`targetMethod`	No	HTTP method	GET
`targetHeaders`	No	Additional headers to send to target

Schema Changelog

Changes observed during successful MCP inspections.

First observedJan 31, 2026

TDQS

B3.4/5.0

Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description must disclose behavioral traits. It mentions 'automatic payment' and pricing, but omits critical behaviors such as the two-step 402 challenge flow (initial response then payment proof), the requirement for a funded wallet, and the fact that this will actually spend USDC. The paymentProof parameter in the schema hints at the flow, but the description itself lacks this transparency and side-effect disclosure.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three short, information-dense sentences. It front-loads the primary purpose, then adds pricing and network details. No redundant or extraneous wording. Every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool has moderate complexity (5 params, no output schema, no annotations) and involves financial transactions. The description explains pricing and network but not the overall workflow, prerequisites (e.g., funded wallet), error conditions, or return behavior. The paymentProof parameter implies a two-step process, but the description doesn't provide enough context for an agent to invoke the tool correctly in all scenarios.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents all five parameters with descriptions. The tool description adds no additional parameter-level meaning beyond what's in the schema. Baseline 3 applies because the schema does the heavy lifting and the description doesn't need to compensate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's function: 'Access x402-protected APIs with automatic payment.' This is a specific verb+resource combination that distinguishes it from sibling tools like x402_proxy_price and x402_send. It also adds relevant details about dynamic pricing and USDC on Base, further clarifying its purpose.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies when to use the tool (for accessing x402-protected APIs when automatic payment is desired), but it does not explicitly mention alternatives or exclusions. Sibling tools exist (e.g., x402_proxy_price, x402_send), yet no guidance is given on when to choose one over the other. Usage is inferred but not directly spelled out.

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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