Schemacheck Agent
About
SchemaCheck Agent validates JSON payloads against JSON Schema Draft 7 and 2020-12 standards. Designed for agent-to-agent workflows, it returns structured validation results instantly — including field-level error paths, human-readable summaries, and optionally a corrected payload
Details
- Author
- garyedgington
- Downloads
- 325
- Categories
- AI, API, Developer Tools
Jump to
- Validates JSON payloads against any JSON Schema
- Returns structured errors with JSONPath locations
- Provides plain-English validation summaries
- Suggests corrected payloads on paid endpoint
- Supports strict, normal, and lenient validation modes
- MCP Streamable HTTP and REST + x402 access modes
Setting up with Highlight
This MCP is not yet compatible with Highlight’s one-click setup. However, you can still use it with Highlight by following these steps:
- Download and install Highlight from highlightai.com/download
- Navigate to the plugins tab and select "Add Custom Plugin"
-
Configure the plugin with the settings below
Plugin Name
Schemacheck AgentCommand (node, npx, python, etc.)Please refer to the README for specific instructions on how to obtain API keys or other required environment variables.
- Enable "Start Automatically" if you want the plugin to start when Highlight launches
From the repository
Connect an MCP-compatible client to https://projectx402-production.up.railway.app/mcp for tool-based usage, or call the REST endpoints directly. The free trial endpoint requires no payment; the paid endpoint uses x402 v2 USDC micropayments of $0.005 per call on Base mainnet. MCP tools available are validate_schema (full, with repair) and validate_schema_trial (free, no repair).
validate_schema
Validate a JSON payload against a JSON Schema. Returns whether the payload is valid, a list of structured validation errors, a human-readable summary, and -- when repair=True and the payload is invalid -- a suggested corrected payload. Args: json_schema: A valid JSON Schema object (Draft 2020-12 or Draft-07). payload: The JSON value to validate (object, array, string, number, boolean, or null). strictness: Controls repair aggressiveness. "strict" -- only fill fields that have explicit defaults. "normal" -- fill missing required fields with type defaults. "lenient" -- same as normal (future: may coerce types). repair: When True and the payload is invalid, attempt to produce a suggested_payload that satisfies the schema. explain: When True, include a human-readable explanation in summary. Returns: valid (bool), errors (list), summary (str), suggested_payload (any|null), confidence (float), meta (dict).
validate_schema_trial
Validate a JSON payload against a JSON Schema (free trial, no repair). Identical to validate_schema but repair suggestions are always disabled. Use this for lightweight checks where a corrected payload is not needed. Args: json_schema: A valid JSON Schema object (Draft 2020-12 or Draft-07). payload: The JSON value to validate. explain: When True, include a human-readable explanation in summary. Returns: valid (bool), errors (list), summary (str), suggested_payload (null), confidence (float), meta (dict).
Claude Desktop / Cursor
Paste into your MCP client config file to install this server.
{
"mcpServers": {
"schemacheck agent": {
"schemacheck-agent": {
"url": "https://projectx402-production.up.railway.app/sse"
}
}
}
}McpServers
{
"schemacheck-agent": {
"url": "https://projectx402-production.up.railway.app/sse"
}
}SchemaCheck Agent
A machine-native paid API for validating JSON payloads against JSON Schema. Live endpoint:https://projectx402-production.up.railway.app
MCP endpoint: https://projectx402-production.up.railway.app/mcp
---
What it does
Send a JSON Schema and a JSON payload. Get back a structured validation result: whether the payload is valid, a list of errors with JSONPath locations, a plain-English summary, and optionally a suggested corrected payload. Built for autonomous agents, backend pipelines, and developers who need reliable, cheap, per-call JSON validation without managing a library dependency. Supports two access modes: - MCP tools via Streamable HTTP — connect any MCP-compatible client directly, fiat billing via MCP-Hive - REST + x402 — HTTP endpoint with USDC micropayment on Base mainnet ($0.005/call) ---Endpoints
| Endpoint | Payment | Repair | Limit | |---|---|---|---| |/mcp (MCP Streamable HTTP) | Fiat via MCP-Hive | Yes (validate_schema) | None |
| POST /v1/schema-check | x402 USDC ($0.005) | Yes | None |
| POST /v1/schema-check/trial | Free | No | 32KB request body |
| GET /health | Free | — | — |
---
Quickstart — MCP (recommended for AI agents)
Add to your MCP client config: ``json
{
"mcpServers": {
"schemacheck": {
"url": "https://projectx402-production.up.railway.app/mcp"
}
}
}
`
Two tools are available: validate_schema (full, with repair) and validate_schema_trial (free, no repair). See docs/agent_quickstart.md for a full Python MCP client example.
---
Quickstart — trial (no payment)
`bash
curl -X POST https://projectx402-production.up.railway.app/v1/schema-check/trial \
-H "Content-Type: application/json" \
-d '{
"json_schema": {
"type": "object",
"required": ["name", "email"],
"properties": {
"name": {"type": "string"},
"email": {"type": "string", "format": "email"}
},
"additionalProperties": false
},
"payload": {
"name": "Ada Lovelace",
"email": "not-an-email"
}
}'
`
Response:
`json
{
"valid": false,
"errors": [
{
"path": "/email",
"code": "format",
"message": "'not-an-email' is not a valid email address.",
"schema_path": "/properties/email/format"
}
],
"summary": "The payload failed validation. 1 error found.",
"suggested_payload": null,
"confidence": 0.9,
"meta": {
"strictness": "normal",
"repair_attempted": false,
"engine": "jsonschema",
"schema_draft": "auto"
}
}
`
---
Quickstart — paid endpoint (x402)
The paid endpoint requires an x402 v2 USDC micropayment of $0.005 per call on Base mainnet.
Payment flow:
1. Send request to POST /v1/schema-check without payment headers.
2. Receive 402 Payment Required with x402Version=2 and payment details.
3. Sign and send payment via PAYMENT-SIGNATURE header.
4. Receive 200 with validation result.
See docs/agent_quickstart.md for a full Python example with x402 payment handling.
---
Request fields
| Field | Type | Required | Default | Description |
|---|---|---|---|---|
| json_schema | object | yes | — | JSON Schema document |
| payload | any | yes | — | The JSON value to validate |
| strictness | string | no | "normal" | "strict", "normal", or "lenient" |
| repair | boolean | no | false | Return a suggested corrected payload if possible |
| explain | boolean | no | true | Include plain-English summary |
---
Response fields
| Field | Type | Description |
|---|---|---|
| valid | boolean | true if payload passes schema validation |
| errors | array | Structured validation errors; empty when valid |
| summary | string | Plain-English summary (null if explain=false) |
| suggested_payload | any / null | Corrected payload suggestion (paid endpoint + repair=true only) |
| confidence | float | Confidence score 0–1 |
| meta | object | Engine, strictness, and repair metadata |
---
Error codes
required · type · format · enum · additionalProperties · minimum · maximum · minLength · maxLength · pattern · items · oneOf · anyOf · allOf · unknown
---
Pricing
| Mode | Price |
|---|---|
| Trial (/v1/schema-check/trial) | Free |
| Paid (/v1/schema-check) | $0.005 USDC per call |
Payment is handled via the x402 protocol — an HTTP-native micropayment standard using USDC on Base.
---
Health check
`bash
curl https://projectx402-production.up.railway.app/health
`
`json
{"status": "ok", "service": "schemacheck-agent", "version": "0.3.0"}
`
---
Reporting issues
If you encounter unexpected responses, payment errors, or validation bugs, please open a GitHub issue.
Include:
- The endpoint called (/v1/schema-check or /v1/schema-check/trial)
- The request body (redact any sensitive data)
- The response received
- The X-Request-ID` header value from the response if available
---
Further reading
- docs/agent_quickstart.md — Full integration guide: MCP tools, x402 payment, trial endpoint - api_contract.md — Full API contract and error shape reference - docs/x402_real_flow.md — x402 v2 payment flow detailsSign in to leave a review
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