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Repair malformed JSON from LLM/agent output; optional JSON Schema coercion. Free + x402 paid.
Repair malformed JSON from LLM/agent output; optional JSON Schema coercion. Free + x402 paid.
Remote endpoints: streamable-http: https://jsonaut.jsonaut-shaurya.workers.dev/mcp
Jsonaut is a well-structured JSON repair service with thoughtful security design. Authentication is appropriately scoped to paid operations via x402 micropayments, and the codebase shows good defensive practices around input handling and credential management. Minor code quality issues (broad exception handling, verbose error messages) and an external dependency on x402 facilitators for payment verification do not significantly impact the security posture. Permissions align well with the service's stated purpose. Supply chain analysis found 9 known vulnerabilities in dependencies (2 critical, 2 high severity).
8 files analyzed · 14 issues found
Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.
This plugin requests these system permissions. Most are normal for its category.
Available as Local & Remote
This plugin can run on your machine or connect to a hosted endpoint. during install.
From the project's GitHub README.
JSON repair & validation built for AI agents as the customer. Send possibly-malformed JSON (LLM tool-call output, another agent's message, a flaky upstream), get back parsed, schema-valid JSON.
Business context, market research, and the full 3-day plan live in IDEA.md and PLAN.md.
npm install
npm test # 27 tests: repair battery, schema coercion, HTTP API, MCP protocol
npm run dev # http://localhost:8787 — demo page + API + MCP endpoint
Try it:
curl -s -X POST http://localhost:8787/v1/repair \
-H "content-type: application/json" \
-d "{\"input\": \"{'name': 'alice', 'count': '42',}\", \"schema\": {\"type\":\"object\",\"properties\":{\"count\":{\"type\":\"number\"}}}}"
{
"valid": true,
"repaired": { "name": "alice", "count": 42 },
"method": "deterministic-repair",
"changes": ["repaired JSON syntax (jsonrepair)", "$.count: coerced string \"42\" to number"]
}
| Route | What it does |
|---|---|
POST /v1/repair | Repair + optional schema validation/coercion. Body: {input, schema?, allow_llm_fallback?} |
POST /v1/validate | Validate only, no repair. Body: {input, schema} |
POST /mcp | MCP server (Streamable HTTP, stateless). Tools: repair_json, validate_json |
GET / | Interactive demo page |
GET /llms.txt | Agent-readable capability + pricing description |
GET /openapi.yaml | OpenAPI 3.1 spec |
Response method values: direct (was already valid), deterministic-repair (free fix), llm-repair (paid fix), failed. changes[] lists every modification so callers can audit what was done to their data.
claude mcp add --transport http jsonaut https://YOUR-DEPLOYMENT/mcp
Or in any MCP client config:
{ "mcpServers": { "jsonaut": { "type": "http", "url": "https://YOUR-DEPLOYMENT/mcp" } } }
For the paid tier, clients pay via x402 and retry with the X-PAYMENT header (the payment receipt). No accounts or API keys — agents pay per call.
/v1/repair with allow_llm_fallback: true; deterministic repair fails.402 with an x402 accepts array (USDC on Base, amount = PRICE_USD).X-PAYMENT header; server verifies via the facilitator, runs the LLM repair, and settles only if the repair succeeds.| Env var | Purpose | Required for |
|---|---|---|
OPENROUTER_API_KEY | Enables the paid LLM-fallback tier (via OpenRouter; free model by default) | Paid tier |
OPENROUTER_MODEL | Override the model (default meta-llama/llama-3.3-70b-instruct:free) | — |
X402_PAY_TO | Wallet address on Base receiving USDC | x402 rail |
X402_NETWORK | base or base-sepolia (default base) | x402 rail |
FACILITATOR_URL | x402 facilitator for verify/settle | x402 rail |
FREE_DAILY_LIMIT | Free calls per IP per day (default 100) | — |
PRICE_USD | Paid-tier price (default 0.01) | — |
DEV_ALLOW_FREE_LLM | true opens the paid tier for local dev only | — |
Local dev secrets go in a .dev.vars file (git-ignored) or your shell env.
npx wrangler login
npx wrangler kv namespace create KV # then paste the id into wrangler.toml
npx wrangler secret put OPENROUTER_API_KEY
npx wrangler deploy
The same codebase runs on Node for local dev (npm run dev) and on Workers in production — storage falls back to in-memory when no KV binding exists.
src/core/ pipeline.ts (repair engine) · coerce.ts (schema coercion) · llm.ts (paid tier)
src/http/ app.ts (routes) · payment.ts (x402 rail) · ratelimit.ts · demo.ts · billing.ts (parked, unused)
src/mcp/ server.ts (stateless Streamable HTTP MCP server)
src/worker.ts Cloudflare Workers entry
src/dev.ts Node dev entry
test/ full battery: broken-JSON cases, coercion, HTTP, MCP protocol
$ref or oneOf/anyOf branches.FACILITATOR_URL); there is no on-chain verification built in.Be the first to review this server!
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