How to Clean Messy LLM JSON Output Without Regex Hell

#api #regex #llm #productivity

You ask an LLM for JSON. It returns:

{
  "name": "John Doe",
  "email": "john@example.com",
  "phone": "555-1234",
  "notes": "Customer called about billing issue -- needs follow-up",
  "tags": ["billing", "urgent"]
}

Looks clean. But paste it into JSON.parse() and boom:

SyntaxError: Unexpected token } in JSON at position 147

The culprit? Trailing comma after the last property. Or maybe it wrapped the whole thing in markdown code fences. Or used single quotes. Or included a comment. Or got cut off mid-token.
You reach for regex. replace(/,\s*}/g, '}') fixes trailing commas. But then you hit markdown fences. Then single quotes. Then a stray // comment. Then a truncated string. Each fix breaks something else.

There's a better way.

Why Existing Tools Fail

Tool	Fails On
Regex	Nested objects, escaped quotes, partial truncation
`jq`	Invalid JSON (trailing commas, comments, single quotes)
Python `json.loads()`	Strict — any violation throws
Online formatters	Manual copy-paste, not automatable
Custom Python scripts	Maintenance burden, edge cases

The pattern: every tool assumes valid JSON. LLM output is almost JSON.

The API Approach: One Call, Pipeline of Fixes

Instead of chaining fragile fixes, define a pipeline — ordered transforms that each handle one class of mess.

curl -X POST https://textforge.co/v1/run \
  -H "Content-Type: application/json" \
  -d '{
    "input": "{name: \"John\", email: \"john@example.com\",}",
    "pipeline": ["removespecial", "removemultiple"]
  }'

Response:

{
  "success": true,
  "input": "{name: \"John\", email: \"john@example.com\",}",
  "pipeline": ["removespecial", "removemultiple"],
  "result": "{\"name\": \"John\", \"email\": \"john@example.com\"}",
  "steps": [
    {"step": 1, "action": "removespecial", "result": "{\"name\": \"John\", \"email\": \"john@example.com\"}"},
    {"step": 2, "action": "removemultiple", "result": "{\"name\": \"John\", \"email\": \"john@example.com\"}"}
  ],
  "execution_time_ms": 3
}