Jsonaut
@shoggi211
Repair malformed JSON from LLM tool calls and agent-to-agent handoffs — fixes trailing commas, single quotes, truncation, markdown code fences, comments, and python literals, and can validate/coerce the result against a JSON Schema. Free deterministic tier; pay-per-call LLM fallb
Overview
What is Jsonaut?
Jsonaut is a tool that repairs malformed JSON produced by LLM tool calls and agent-to-agent handoffs. It fixes issues like trailing commas, single quotes, truncation, markdown code fences, comments, and Python literals, and can validate/coerce the result against a JSON Schema. It is built for developers working with LLM-generated JSON that needs to be clean.
How to use Jsonaut?
You can use Jsonaut via its MCP server (exposing repair_json and validate_json tools), its REST API, or by installing its local-first npm or Python client libraries. Most JSON fixes happen deterministically without external calls.
Key features of Jsonaut
- Repairs common JSON malformations from LLM output (trailing commas, single quotes, truncation, etc.)
- Validates and coerces results against a JSON Schema
- Free deterministic tier for most fixes
- Pay-per-call LLM fallback via x402 (USDC on Base)
- Exposes MCP endpoints (
repair_json,validate_json), REST API, and local npm/Python clients
Use cases of Jsonaut
- Cleaning malformed JSON from LLM tool call responses
- Fixing JSON during agent-to-agent handoffs
- Ensuring LLM-generated JSON conforms to a specified JSON Schema
- Adding a recovery layer in LLM pipelines without full retries
FAQ from Jsonaut
What types of JSON issues does Jsonaut fix?
It corrects trailing commas, single quotes, truncations, markdown code fences, comments, and Python literals in JSON output from LLMs.
Is there a free tier?
Yes, a free deterministic tier handles most fixes locally without any payment. A paid LLM fallback is available via x402 (USDC on Base) for edge cases.
How can I access Jsonaut?
Jsonaut is available as an MCP server, a REST API, and as local-first npm or Python client libraries.
Does Jsonaut require an internet connection?
The deterministic tier works offline with the local npm/Python clients. The LLM fallback (x402) requires an internet connection and a USDC payment on Base.
