Beauty & Personal Care · x402 · early usage

Stockfish cloud evaluation for a FEN position

Stockfish cloud evaluation for a FEN position. Returns depth, evaluation, and principal variation(s) when Lichess has the position cached.

by chess402.vercel.app · discovered, not yet claimed by its owner · updated 2026-10-02

30d calls1

30d payers1

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

Stockfish cloud evaluation for a FEN position. Returns depth, evaluation, and principal variation(s) when Lichess has the position cached.

Tags: bazaar

Call contract

Method: POST
Input: json
Output: json
Last paid call: 2026-10-02

Input example from Bazaar metadata

{
  "fen": "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
  "multiPv": 1
}

Output example

{
  "depth": 22,
  "fen": "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
  "knodes": 13683,
  "pvs": [
    {
      "cp": 27,
      "moves": "e2e4 c7c5 g1f3 d7d6 d2d4 c5d4"
    }
  ]
}

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/55093.json for the price and payment options.
Pay. Call GET https://chess402.vercel.app/api/cloud-eval. 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: $0.005 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base
Demand: 1 calls · 1 unique payers in 30d (public x402 Bazaar data)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.005	0xfbd46201267609ad3c66bd1b99b7f1cc80b1852f	300s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xfbd46201267609ad3c66bd1b99b7f1cc80b1852f",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "5000",
    "amountUsd": 0.005,
    "maxTimeoutSeconds": 300
  }
]

Schemas

Output schema (JSON Schema)

{
  "properties": {
    "example": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "additionalProperties": {},
      "description": "Cloud-eval response: depth, knodes, and principal variations.",
      "properties": {
        "depth": {
          "description": "Search depth in plies.",
          "maximum": 9007199254740991,
          "minimum": -9007199254740991,
          "type": "integer"
        },
        "fen": {
          "description": "Echoed FEN that was evaluated.",
          "type": "string"
        },
        "knodes": {
          "description": "Kilonodes searched.",
          "maximum": 9007199254740991,
          "minimum": -9007199254740991,
          "type": "integer"
        },
        "pvs": {
          "description": "Principal variations (one per multiPv).",
          "items": {
            "additionalProperties": {},
            "properties": {
              "cp": {
                "description": "Evaluation in centipawns from the side-to-move POV.",
                "maximum": 9007199254740991,
                "minimum": -9007199254740991,
                "type": "integer"
              },
              "mate": {
                "description": "Mate-in-N from the side-to-move POV, when applicable.",
                "maximum": 9007199254740991,
                "minimum": -9007199254740991,
                "type": "integer"
              },
              "moves": {
                "description": "Space-separated UCI moves of the principal variation.",
                "type": "string"
              }
            },
            "required": [
              "moves"
            ],
            "type": "object"
          },
          "type": "array"
        }
      },
      "required": [
        "fen",
        "pvs"
      ],
      "type": "object"
    },
    "type": {
      "type": "string"
    }
  },
  "required": [
    "type"
  ],
  "type": "object"
}

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

{
  "example": {
    "depth": 0,
    "fen": "string",
    "knodes": 0,
    "pvs": [
      {
        "cp": 0,
        "mate": 0,
        "moves": "string"
      }
    ]
  },
  "type": "string"
}

Examples

curl

curl -X POST 'https://chess402.vercel.app/api/cloud-eval' -H 'Content-Type: application/json' --data '{"fen":"rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1","multiPv":1}'
# -> 402 Payment Required; read PAYMENT-REQUIRED
# retry the identical request with PAYMENT-SIGNATURE

JavaScript

const res = await fetch("https://chess402.vercel.app/api/cloud-eval", {
  "method": "POST",
  "headers": {
    "content-type": "application/json"
  },
  "body": "{\"fen\":\"rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1\",\"multiPv\":1}"
});
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
import json
res = httpx.request("POST", "https://chess402.vercel.app/api/cloud-eval", json=json.loads("{\"fen\":\"rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1\",\"multiPv\":1}"))
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: chess402.vercel.app
Endpoint: https://chess402.vercel.app/api/cloud-eval
Machine-readable: /resources/55093.json