# x402 Paid MCP Authorization Bridge

> x402 Paid MCP Authorization Bridge is a paid API for AI agents from gpt55.558686.xyz, paid per call via x402, $0.012/call, status unknown (last checked 2026-09-14).

Generates a complete authorization package (MCP scope contract, x402 quote gate, retry plan, receipt gate, client policy JSON, audit schema, and fail-closed snippet) for agents needing explicit authorization before spending USDC on paid MCP tools.

## Facts

- Endpoint: POST https://gpt55.558686.xyz/v1/tools/x402-paid-mcp-authorization-bridge
- Price: $0.012/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-paid-mcp-authorization-bridge-6637f6f8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_SgXkEiO_XW2idUa_6Bh1K

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-paid-mcp-authorization-bridge-6637f6f8 -d '<json body>'
```

Example prompt: Generate a full authorization bridge for the paid MCP tool at https://mcp.example.com/v1/tools/my-tool — the MCP server is https://mcp.example.com, authorization scope is 'tools:read:my-tool', max spend is $0.05 per call, daily budget is $2.00 USDC, expected asset is USDC on Base, and I need receipt evidence required and human approval for the first payment.

## When to prefer this

Use this endpoint when an AI agent needs to generate a complete, deterministic authorization policy before allowing real USDC spending on a paid MCP tool — especially when you need spend caps, receipt verification, human approval gates, audit trails, and fail-closed behavior baked into a single copy-paste package. Prefer this over manual policy construction or general-purpose LLM prompting when you need deterministic, structured output with no upstream model calls.

## Known failure modes

- Missing required fields (paid_tool_url, authorization_scope, mcp_server_url) returns a validation error
- max_usdc_per_call or daily_budget_usdc out of allowed range returns schema error
- expected_asset or expected_network values unrecognized may produce incomplete gate configuration
- Input exceeding 700000 characters returns a payload-too-large error
- Malformed service_url or mcp_server_url returns URL validation failure

## How this service works

Turn a paid MCP tool route, buyer authorization scope, x402 quote expectations, spend caps, and receipt requirements into a copy-paste authorization bridge: MCP scope contract, x402 quote gate, same-request retry plan, receipt-bound execution gate, client policy JSON, audit schema, and fail-closed runtime snippet. Built for agents that need explicit authorization before spending real USDC on paid MCP tools. This deterministic endpoint does not call an upstream model and never asks for private keys. Pay up to $0.012 per request with x402 USDC on Base. Public paid calls are limited to 700000 input characters and 4096 output tokens.

## Output

Returns a copy-paste authorization package including: an MCP scope contract, an x402 quote gate configuration, a same-request retry plan, a receipt-bound execution gate, a client policy JSON, an audit schema, and a fail-closed runtime code snippet — all structured to enforce explicit authorization before the agent spends real USDC on the specified paid MCP tool.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "method": {
   "enum": [
    "GET",
    "POST",
    "PUT",
    "PATCH",
    "DELETE"
   ],
   "type": "string"
  },
  "tool_name": {
   "type": "string",
   "maxLength": 160,
   "minLength": 1
  },
  "buyer_agent": {
   "type": "string",
   "maxLength": 240
  },
  "service_url": {
   "type": "string",
   "maxLength": 2048,
   "minLength": 1
  },
  "paid_tool_url": {
   "type": "string",
   "maxLength": 2048,
   "minLength": 1
  },
  "expected_asset": {
   "type": "string",
   "maxLength": 40
  },
  "mcp_server_url": {
   "type": "string",
   "maxLength": 2048,
   "minLength": 1
  },
  "allowed_origins": {
   "type": "array",
   "items": {
    "type": "string",
    "maxLength": 2048
   },
   "maxItems": 30
  },
  "expected_pay_to": {
   "type": "string",
   "maxLength": 120
  },
  "expected_network": {
   "type": "string",
   "maxLength": 80
  },
  "daily_budget_usdc": {
   "type": "number",
   "maximum": 10000,
   "minimum": 0.0001
  },
  "max_usdc_per_call": {
   "type": "number",
   "maximum": 100,
   "minimum": 0.0001
  },
  "authorization_scope": {
   "type": "string",
   "maxLength": 240,
   "minLength": 1
  },
  "idempotency_key_header": {
   "type": "string",
   "maxLength": 80
  },
  "require_receipt_evidence": {
   "type": "boolean"
  },
  "require_human_approval_first_payment": {
   "type": "boolean"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-paid-mcp-authorization-bridge-6637f6f8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from gpt55.558686.xyz](https://www.zero.xyz/host/gpt55.558686.xyz/llms.txt)