MCP Tool · x402 · early usage

Auto-detect a public MCP endpoint era, fingerprint its complete normalized tools/list s…

Auto-detect a public MCP endpoint era, fingerprint its complete normalized tools/list schema contract and optionally compare it with a caller-provided previous SHA-256 hash. Cosmetic descriptions are excluded so text-only edits do not trigger contract drift.…

by http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run · discovered, not yet claimed by its owner · updated 2026-10-10

30d calls2

30d payers2

MethodPOST

Outputjson

Mirrored from Coinbase's public x402 Bazaar. The description is the provider's own text and has not been reviewed here; the payment requirements are copied as published.

What it does

Tags: mcp · contract · monitoring · bazaar

Call contract

Method: POST
Input: json
Output: json
Last paid call: 2026-10-10

Input example from Bazaar metadata

{
  "previous_hash": "0000000000000000000000000000000000000000000000000000000000000000",
  "url": "https://http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run/fixtures/mcp"
}

Output example

{
  "capability": "mcp.changed",
  "data": {
    "auth_required": false,
    "changed": false,
    "new_hash": "0000000000000000000000000000000000000000000000000000000000000000",
    "previous_hash": "0000000000000000000000000000000000000000000000000000000000000000",
    "protocol_era": "modern",
    "protocol_version": "example",
    "reachable": false,
    "schema_valid": false,
    "scope": "mcp_tools_schema_contract_change_only",
    "tool_count": 0,
    "transport": "http-jsonrpc",
    "url": "example",
    "warnings": []
  },
  "meta": {
    "cache": "miss",
    "checked_at": "2026-01-01T00:00:00.000Z",
    "duration_ms": 0,
    "provider": "mcp-contract"
  },
  "ok": true,
  "version": "1"
}

Use with an agent

Discover. Agents find this listing with GET https://bazaar.saylorinnovations.com/discovery/search?query=…, the MCP tool search_resources, or /discovery/resources.
Inspect. Fetch /resources/33961.json for the price and payment options.
Pay. Call GET https://http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run/mcp/changed. The provider answers 402 with its payment requirements. An x402 client signs one of the options below and retries with PAYMENT-SIGNATURE.
Execute. The provider returns 200 with the data. Agent Bazaar is not in the request path and never sees your payment.

For humans

You don't need an account or an API key; you need a wallet holding a small amount of USDC on Base, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.004 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base
Demand: 2 calls · 2 unique payers in 30d (public x402 Bazaar data)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.004	0xf9c2a7255E7C51D7BF38331DcFC23Ba881cF61Ba	120s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xf9c2a7255E7C51D7BF38331DcFC23Ba881cF61Ba",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "4000",
    "amountUsd": 0.004,
    "maxTimeoutSeconds": 120
  }
]

Schemas

Output schema (JSON Schema)

{
  "properties": {
    "example": {
      "additionalProperties": false,
      "properties": {
        "capability": {
          "const": "mcp.changed",
          "description": "Public capability value used to scope this lookup."
        },
        "data": {
          "additionalProperties": false,
          "description": "Public data value used to scope this lookup.",
          "properties": {
            "auth_required": {
              "description": "Public auth required value used to scope this lookup.",
              "type": "boolean"
            },
            "changed": {
              "description": "Public changed value used to scope this lookup.",
              "type": [
                "boolean",
                "null"
              ]
            },
            "new_hash": {
              "description": "Earlier result hash used to detect a material change.",
              "pattern": "^[a-fA-F0-9]{64}$",
              "type": [
                "string",
                "null"
              ]
            },
            "previous_hash": {
              "description": "Earlier result hash used to detect a material change.",
              "pattern": "^[a-fA-F0-9]{64}$",
              "type": [
                "string",
                "null"
              ]
            },
            "protocol_era": {
              "description": "Public protocol era value used to scope this lookup.",
              "enum": [
                "modern",
                "legacy",
                null
              ],
              "type": [
                "string",
                "null"
              ]
            },
            "protocol_version": {
              "description": "Public protocol version value used to scope this lookup.",
              "type": [
                "string",
                "null"
              ]
            },
            "reachable": {
              "description": "Public reachable value used to scope this lookup.",
              "type": "boolean"
            },
            "schema_valid": {
              "description": "Public schema valid value used to scope this lookup.",
              "type": [
                "boolean",
                "null"
              ]
            },
            "scope": {
              "const": "mcp_tools_schema_contract_change_only",
              "description": "Public scope value used to scope this lookup."
            },
            "tool_count": {
              "description": "Public tool count value used to scope this lookup.",
              "minimum": 0,
              "type": [
                "integer",
                "null"
              ]
            },
            "transport": {
              "description": "Public transport value used to scope this lookup.",
              "enum": [
                "http-jsonrpc",
                "sse"
              ]
            },
            "url": {
              "description": "Public HTTP(S) URL to inspect, resolve, or compare.",
              "type": "string"
            },
            "warnings": {
              "description": "Public warnings value used to scope this lookup.",
              "items": {
                "type": "string"
              },
              "type": "array"
            }
          },
          "required": [
            "url",
            "changed",
            "previous_hash",
            "new_hash",
            "reachable",
            "auth_required",
            "protocol_era",
            "protocol_version",
            "transport",
            "tool_count",
            "schema_valid",
            "warnings",
            "scope"
          ],
          "type": "object"
        },
        "meta": {
          "additionalProperties": false,
          "description": "Public meta value used to scope this lookup.",
          "properties": {
            "cache": {
              "description": "Public cache value used to scope this lookup.",
              "enum": [
                "hit",
                "miss",
                "bypass"
              ]
            },
            "checked_at": {
              "description": "Public checked at value used to scope this lookup.",
              "type": "string"
            },
            "duration_ms": {
              "description": "Public duration ms value used to scope this lookup.",
              "minimum": 0,
              "type": "integer"
            },
            "provider": {
              "description": "Public provider value used to scope this lookup.",
              "type": [
                "string",
                "null"
              ]
            }
          },
          "required": [
            "provider",
            "checked_at",
            "cache",
            "duration_ms"
          ],
          "type": "object"
        },
        "ok": {
          "const": true,
          "description": "Public ok value used to scope this lookup."
        },
        "version": {
          "const": "1",
          "description": "Package version whose public metadata should be checked."
        }
      },
      "required": [
        "ok",
        "capability",
        "version",
        "data",
        "meta"
      ],
      "type": "object"
    },
    "type": {
      "type": "string"
    }
  },
  "required": [
    "type"
  ],
  "type": "object"
}

Example shape — generated from the schema, not a captured live response

{
  "example": {
    "capability": null,
    "data": {
      "auth_required": true,
      "changed": true,
      "new_hash": "string",
      "previous_hash": "string",
      "protocol_era": "modern",
      "protocol_version": "string",
      "reachable": true,
      "schema_valid": true,
      "scope": null,
      "tool_count": 0,
      "transport": "http-jsonrpc",
      "url": "string",
      "warnings": [
        "string"
      ]
    },
    "meta": {
      "cache": "hit",
      "checked_at": "string",
      "duration_ms": 0,
      "provider": "string"
    },
    "ok": null,
    "version": null
  },
  "type": "string"
}

Examples

curl

curl "https://http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run/mcp/changed"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run/mcp/changed");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

Python

import httpx
res = httpx.get("https://http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run/mcp/changed")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header

Details

Provider: http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run
Endpoint: https://http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run/mcp/changed
Machine-readable: /resources/33961.json