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x402 Payment Gateway

wever_x402-payment-gateway

Paid URL: 0.10 USDC per call on Base; 10 signed-wallet free calls shared over rolling 30 days. Read the backend 402 body for x402 terms. Check an EOA payment signature and read its Base USDC nonce, balance and chain time. Operating boundary: Supply the payment signature and its terms. Read the signature check, nonce, balance and chain time. An agent uses these observations before settlement; a human reviews the payment terms in the wallet. POST /api/x402-payment-gateway. Existing product credentials, signed mandates, and single-use action grants remain required where applicable. This adapter grants no authority and never supplies server credentials. This current money service follows its published inspection, policy evaluation or private invoice contract. Payment is an API access fee and grants no spending authority.

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": {
      "mode": "<mode>",
      "target_product": "<target_product>",
      "payment": "<payment>"
    },
    "name": "wever_x402-payment-gateway"
  }
}

Input Schema

NameRequiredDescriptionDefault
modeYes
paymentYes
target_productYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed11 schema fields changed
    • changedInput schema / additionalProperties
      Previous value: -trueNew value: +false
    • removedInput schema / description
      Removed value: -"The existing product POST body. Supply its documented mode, arguments, and required signed authority or grant. The product validates its full contract."
    • removedInput schema / maxProperties
      Removed value: -64
    • removedInput schema / minProperties
      Removed value: -1
    • addedInput schema / properties / mode / const
      Added value: +"inspect_x402_authorization"
    • removedInput schema / properties / mode / maxLength
      Removed value: -128
    • removedInput schema / properties / mode / minLength
      Removed value: -1
    • removedInput schema / properties / mode / type
      Removed value: -"string"
    • addedInput schema / properties / payment
      Added value: +{
      +  "additionalProperties": false,
      +  "properties": {
      +    "accepted": {
      +      "additionalProperties": false,
      +      "properties": {
      +        "amount": {
      +          "pattern": "^(0|[1-9][0-9]{0,77})(?![\\s\\S])",
      +          "type": "string"
      +        },
      +        "asset": {
      +          "pattern": "^0x[0-9a-fA-F]{40}(?![\\s\\S])",
      +          "type": "string"
      +        },
      +        "extra": {
      +          "additionalProperties": false,
      +          "properties": {
      +            "name": {
      +              "const": "USD Coin"
      +            },
      +            "version": {
      +              "const": "2"
      +            }
      +          },
      +          "required": [
      +            "name",
      +            "version"
      +          ],
      +          "type": "object"
      +        },
      +        "maxTimeoutSeconds": {
      +          "maximum": 3600,
      +          "minimum": 1,
      +          "type": "integer"
      +        },
      +        "network": {
      +          "const": "eip155:8453"
      +        },
      +        "payTo": {
      +          "pattern": "^0x[0-9a-fA-F]{40}(?![\\s\\S])",
      +          "type": "string"
      +        },
      +        "scheme": {
      +          "const": "exact"
      +        }
      +      },
      +      "required": [
      +        "scheme",
      +        "network",
      +        "amount",
      +        "asset",
      +        "payTo",
      +        "maxTimeoutSeconds",
      +        "extra"
      +      ],
      +      "type": "object"
      +    },
      +    "payload": {
      +      "additionalProperties": false,
      +      "properties": {
      +        "authorization": {
      +          "additionalProperties": false,
      +          "properties": {
      +            "from": {
      +              "pattern": "^0x[0-9a-fA-F]{40}(?![\\s\\S])",
      +              "type": "string"
      +            },
      +            "nonce": {
      +              "pattern": "^0x[0-9a-fA-F]{64}(?![\\s\\S])",
      +              "type": "string"
      +            },
      +            "to": {
      +              "pattern": "^0x[0-9a-fA-F]{40}(?![\\s\\S])",
      +              "type": "string"
      +            },
      +            "validAfter": {
      +              "pattern": "^(0|[1-9][0-9]{0,77})(?![\\s\\S])",
      +              "type": "string"
      +            },
      +            "validBefore": {
      +              "pattern": "^(0|[1-9][0-9]{0,77})(?![\\s\\S])",
      +              "type": "string"
      +            },
      +            "value": {
      +              "pattern": "^(0|[1-9][0-9]{0,77})(?![\\s\\S])",
      +              "type": "string"
      +            }
      +          },
      +          "required": [
      +            "from",
      +            "to",
      +            "value",
      +            "validAfter",
      +            "validBefore",
      +            "nonce"
      +          ],
      +          "type": "object"
      +        },
      +        "signature": {
      +          "pattern": "^0x[0-9a-fA-F]{130}(?![\\s\\S])",
      +          "type": "string"
      +        }
      +      },
      +      "required": [
      +        "signature",
      +        "authorization"
      +      ],
      +      "type": "object"
      +    },
      +    "resource": {
      +      "additionalProperties": false,
      +      "properties": {
      +        "description": {
      +          "maxLength": 256,
      +          "type": "string"
      +        },
      +        "mimeType": {
      +          "const": "application/json"
      +        },
      +        "url": {
      +          "maxLength": 256,
      +          "minLength": 1,
      +          "type": "string"
      +        }
      +      },
      +      "required": [
      +        "url",
      +        "description",
      +        "mimeType"
      +      ],
      +      "type": "object"
      +    },
      +    "x402Version": {
      +      "const": 2
      +    }
      +  },
      +  "required": [
      +    "x402Version",
      +    "resource",
      +    "accepted",
      +    "payload"
      +  ],
      +  "type": "object"
      +}
    • addedInput schema / properties / target_product
      Added value: +{
      +  "enum": [
      +    "diligenceops-paid-run",
      +    "agent-daily-operator-brief",
      +    "mcp-diligence-rail",
      +    "agent-work-order-rail",
      +    "agent-paid-workflow",
      +    "unified-agent-checkout",
      +    "agent-allowance-console",
      +    "agent-work-order-exchange",
      +    "proof-relay",
      +    "delegated-authority",
      +    "x402-payment-gateway",
      +    "payment-authority-inspector",
      +    "agent-invoice-rail",
      +    "agent-budget-guard"
      +  ]
      +}
    • addedInput schema / required
      Added value: +[
      +  "mode",
      +  "target_product",
      +  "payment"
      +]
  2. First observed

TDQS

B3.1/5.0
Behavior4/5

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

Annotations declare a non-read-only, open-world call, and the description adds meaningful context beyond them: cost (0.10 USDC per call on Base), a free-call quota (10 signed-wallet calls per rolling 30 days), and an explicit authority disclaimer ('grants no authority and never supplies server credentials'). It does not describe the response payload or failure modes, keeping it short of a 5.

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

Conciseness3/5

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

The pricing/terms sentence is usefully front-loaded, but the closing sentence about 'published inspection, policy evaluation or private invoice contract' is vague boilerplate that adds no callable information. The operant instruction sits mid-paragraph rather than leading.

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

Completeness3/5

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

For a 3-parameter nested schema with no output schema and 0% field descriptions, the description does tell the agent what will be observed (signature check, nonce, balance, chain time), which partially substitutes for an output schema. It still leaves the required 'mode' and 'target_product' selection unexplained, so completeness is only partial.

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

Parameters2/5

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

Schema description coverage is 0% and the schema is deeply nested, so the description must carry parameter meaning. It only alludes to supplying 'the payment signature and its terms'; the 'mode' constant, the 14-value 'target_product' enum, and the relationship between the 402 body and the 'accepted'/'payload' objects are never explained.

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

Purpose3/5

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

The description does state a concrete action — 'Check an EOA payment signature and read its Base USDC nonce, balance and chain time' — but it is buried after pricing copy and an HTTP verb ('POST /api/x402-payment-gateway') that makes it read like a gateway/executor rather than an inspector. The tool name 'payment gateway' further muddies the purpose, and nothing distinguishes it from close siblings like payment-authority-inspector or ap2-mandate-gateway.

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?

'An agent uses these observations before settlement; a human reviews the payment terms in the wallet' gives a real usage context and a hand-off boundary. However, there is no explicit when-not-to-use or named alternative among the many overlapping payment/authority siblings, so routing still requires inference.

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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