MCP.Market

Jsonaut MCP server

online · 100% uptime
by shoggi211·io.github.shoggi211/jsonaut·v0.1.0·1 stars
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Repair malformed JSON from LLM/agent output; optional JSON Schema coercion. Free + x402 paid.

B84/100grade B
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Safety scan
B84/100

full report

Adoption
New

1 stars

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If you have run it, two minutes of your experience saves the next person an afternoon.

Jsonaut tools (4)

write = sends, deletes, buys or posts
  • extract_jsonFree

    Extract JSON embedded in arbitrary text — LLM prose, chat messages, logs, emails — then repair and validate it. Deterministic extraction is free. If no JSON can be located and allow_llm_fallback is true, a paid LLM extracts structured data from the text (requires x402 payment; charged only on success). Pass a JSON Schema to shape the output.

  • infer_schemaFree

    Infer a JSON Schema (draft 2020-12) from an example JSON value. Free and deterministic. Set as_samples=true when the input is an array of example objects of the same shape to merge them into one schema. Turns sample agent/tool output into a reusable schema.

  • repair_jsonFree

    Repair malformed JSON (trailing commas, single quotes, truncation, markdown fences, comments, python literals) and optionally validate/coerce it against a JSON Schema. Deterministic repair is free. If it fails and allow_llm_fallback is true, a paid LLM repair is attempted (requires x402 payment; charged only on success).

  • validate_jsonFree

    Validate a JSON string against a JSON Schema. Free. Returns validity and a list of violations.

Public scan report

scanner v0.1.9 · 2026-09-26 · same rubric, same numbers if you re-run it

no findings
  • –Code scanremote-only server, no package to scann/a
  • Live reliabilityremote reachable in 249ms20/20
  • Tool poisoning4 tool descriptions checked15/15
  • Auth qualityopen endpoint, read-only tools10/15
  • Maintenancelast push 82 days ago12/15
  • Maintainer identityregistry namespace matches repository owner6/10
Overall 84/100. Components that don't apply are left out of the denominator. Any critical finding is an F.RubricAppeal a findingJSON

How Jsonaut compares

Against every graded AI and agents MCP server, from our own scans and uptime checks. Updated after each scan run.

Safety score
84/100
higher than 70% of 4,460 AI and agents servers
Tools
4
the typical AI and agents server has 6
Tools that change things
0%
typical: 0%. Fewer write tools means less an agent can break
Uptime
100%
of our recent checks; the typical remote AI and agents server answers 100%
Response time
47 ms
faster than 96% of 2,331 AI and agents servers
GitHub stars
1
more than 50% of 2,711 AI and agents servers

What its tools let an agent do: 4 read

Install Jsonaut in Claude Code, Cursor or VS Code

claude mcp add --transport http jsonaut https://jsonaut.jsonaut-shaurya.workers.dev/mcp
Add to Cursor

What the publisher says

From the Jsonaut repository's README, as published. We do not edit it. Read it on GitHub

Jsonaut

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.

  • Free tier: deterministic repair — trailing commas, single quotes, truncation, markdown code fences, comments, Python literals — plus JSON Schema validation with type coercion (string→number, defaults, stripping hallucinated fields). Rate-limited per IP.
  • Paid tier: LLM-fallback repair for inputs the deterministic pass can't fix. $0.01/call, charged only on success, paid autonomously per-call via x402 (USDC on Base) — no accounts, no signup.

Business context, market research, and the full 3-day plan live in IDEA.md and PLAN.md.

Quickstart

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"]
}

API

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.

Using it from an agent (MCP)

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.

Payment flow (x402)

  1. Agent calls /v1/repair with allowllmfallback: true; deterministic repair fails.
  2. Server responds 402 with an x402 accepts array (USDC on Base, amount = PRICE_USD).
  3. Agent pays and retries with the X-PAYMENT header; server verifies via the facilitator, runs the LLM repair, and settles only if the repair succeeds.

Configuration

Local dev secrets go in a .dev.vars file (git-ignored) or your shell env.

Deployment (Cloudflare Workers)

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

Shortened. The full README is on GitHub.

Nothing above is checked by us. What we check is on the safety report.

Jsonaut: common questions

Is Jsonaut MCP server safe?
Mostly: it is graded B (84/100). Read the Jsonaut safety report
How do I install Jsonaut?
It runs remotely at jsonaut.jsonaut-shaurya.workers.dev. Add it to Claude Code, Cursor, VS Code or Claude Desktop with the snippets above, or call it through the mcp.market gateway without installing anything.
Does Jsonaut need an API key?
Not as far as the registry entry and our scan can tell: no credentials are declared or required.
Is Jsonaut maintained?
The last commit was 121 days ago (2026-07-06). The latest release is v0.1.0.
Is Jsonaut up?
100% of our last 28 checks got an answer. We check remote servers about four times a day.
What can I use instead of Jsonaut?
Servers from other publishers that do the same job: FireCMS Cloud MCP server, Butterbase AI MCP server and llmtrim MCP server.
How does Jsonaut compare with other AI and agents MCP servers?
safety score 84/100 (higher than 70% of 4,460 AI and agents servers); tools 4 (the typical AI and agents server has 6); tools that change things 0% (typical: 0%. Fewer write tools means less an agent can break). Full comparison.

Alternatives to Jsonaut

Same job from other publishers: the closest match first, then the best rated.

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    A
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  • llmtrim
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