# json-schema-validate

> Validate LLM/agent JSON output against a JSON Schema (2020-12 subset) and auto-repair typical errors: code fences, trailing commas, numbers/booleans as strings, wrong enum case, single value instead of array, null optionals, extra or mis-cased keys, missing defaults. Returns errors, repaired JSON and fixes. POST recommended.

- URL: https://forge-tools.dentreprise.workers.dev/api/json-schema-validate (GET or POST)
- Price: 0.001 USDC on Base (1000 atomic USDC)
- MCP tool: json_schema_validate
- Docs: https://agent-hub.dentreprise.workers.dev/tools/json-schema-validate/

## Parameters

- `schema` (object, required): JSON Schema
- `data` (string, required): JSON value or string to check
- `repair` (string): true (default) / false

## Unpaid example

```bash
curl -sS -D - "https://forge-tools.dentreprise.workers.dev/api/json-schema-validate?schema=%5Bobject+Object%5D&data=%7B%22age%22%3A+%2242%22%7D"
```

## Example 402 challenge

```json
{
  "x402Version": 2,
  "error": "Payment required",
  "resource": {
    "url": "https://forge-tools.dentreprise.workers.dev/api/json-schema-validate",
    "description": "Validate LLM/agent JSON output against a JSON Schema (2020-12 subset) and auto-repair typical errors: code fences, trailing commas, numbers/booleans as strings, wrong enum case, single value instead of array, null optionals, extra or mis-cased keys, missing defaults. Returns errors, repaired JSON and fixes. POST recommended.",
    "mimeType": "application/json"
  },
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:8453",
      "amount": "1000",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "payTo": "0x7B8bf45ac6AcbA6D4CFB626b57D3f5fF3C9C89F7",
      "maxTimeoutSeconds": 120,
      "extra": {
        "name": "USD Coin",
        "version": "2"
      }
    }
  ]
}
```

## Example response

```json
{
  "valid": false,
  "errors": [
    {
      "path": "$.age",
      "msg": "expected integer, got string"
    }
  ],
  "repaired": {
    "age": 42
  },
  "repaired_valid": true
}
```

## Free demo / sample

This tool accepts `?demo=1` on the wave-1 worker (labelled sample, HTTP 200, not live data). The first 3 successful real calls per IP per UTC day are also free.

```bash
curl -sS "https://forge-tools.dentreprise.workers.dev/api/json-schema-validate?schema=%5Bobject+Object%5D&data=%7B%22age%22%3A+%2242%22%7D&demo=1"
```

```json
{
  "demo": true,
  "demo_label": "DEMO / SAMPLE — not live data. This is a labelled example response and was not charged.",
  "charged": false,
  "tool": "/api/json-schema-validate",
  "docs": "https://agent-hub.dentreprise.workers.dev/tools/json-schema-validate/",
  "how_to_get_live_data": "Call the same URL without demo=1. The first 3 successful real calls per IP per UTC day are free; after that attach an x402 v2 PAYMENT-SIGNATURE (USDC on Base).",
  "sample": {
    "valid": false,
    "errors": [
      {
        "path": "$.age",
        "msg": "expected integer, got string"
      }
    ],
    "repaired": {
      "age": 42
    },
    "repaired_valid": true
  }
}
```

## Clients

- JS (x402 v2): `@x402/fetch` + `@x402/evm` (`wrapFetchWithPaymentFromConfig`, `ExactEvmScheme`). The older package `x402-fetch` is deprecated v1.
- Python: PyPI package `x402` (`x402HttpxClient` or `x402_requests`, `register_exact_evm_client`, `EthAccountSigner`).
- MCP: stdio `node src/server.mjs` in [forge-agent-mcp](https://github.com/forge-agent-hub/forge-agent-mcp); hosted Streamable HTTP at https://x402-gateway.forge-x402.workers.dev/mcp (original gateway tools).
- LangChain: wrap those clients with `DynamicStructuredTool` (`@langchain/core`) or `@tool` (`langchain_core`).
- Copy-paste snippets: https://agent-hub.dentreprise.workers.dev/tools/json-schema-validate/ and https://agent-hub.dentreprise.workers.dev/quickstart/