Works with the AI tools you already use
Claude Code
Cursor
Codex CLI
Muse
Dots+22 moreClaude CodeCursorCodex CLIMuseDots
OpenClaw
Manus
Grok
Grok Bot+18 agentsLLM Output JSON Validator
Instantly detects, cleans, and repairs malformed LLM JSON outputs including markdown noise and syntax errors.
Free
LLM Output JSON Validator
Example session with this skill installed
Fix this broken JSON from my LLM: json { 'user_id': 101, 'actions': ['login', 'update',], 'meta': 'Needs "high" priority' }
- Read your context and instructions
- Compiled the llm output json
- Generated the document
[LLM JSON Validation Report]
🔍 Issues Detected:
- Markdown wrappers detected and removed.
- Single quotes replaced with double quotes for keys and values.
- Trailing comma fixed in 'actions' array.
- Internal double quotes in 'meta' value escaped for valid JSON syntax.
✅ Repaired JSON Output:
{
"user_id": 101,
"actions": [
"login",
"update"
],
"meta": "Needs \"high\" priority"
}
💡 Pro-Tip for Prevention:
- Use a Pydantic model or Zod schema in your prompt and explicitly instruct the model to "Output raw JSON without markdown code blocks" to reduce parsing overhead.
[Self-Check]
- Markdown and conversational noise stripped
- Common syntax errors (commas, quotes) repaired
- Final output is strictly valid, parseable JSON
- Actionable prevention tip provided
Next steps
- Copy the repaired JSON into your test suite or API client.
- Update your agent's system instructions to include the provided prevention tip.
- Verify if the
user_idtype (integer) matches your database schema requirements.
llm-output-json-validator.pdf
PDF · document
Example file from a real run - the skill writes it into your workspace.
Connects securely to your tools. The creator never sees your data.
About this skill
The problem
LLMs frequently break production pipelines by returning JSON wrapped in markdown, using trailing commas, or failing to escape special characters. Manually cleaning these outputs for testing or debugging is slow and error-prone.
What it does
- Detects and strips markdown code blocks and conversational text surrounding JSON objects.
- Automatically repairs trailing commas and replaces single quotes with valid double quotes.
- Identifies unescaped special characters and restores missing closing brackets or braces.
- Generates a diagnostic report detailing exactly what failed in the original LLM response.
Why this beats prompting it yourself
General-purpose agents often hallucinate or repeat the same formatting errors when asked to fix them. This skill uses a strict validation logic to ensure the final output is parseable by standard JSON libraries without additional manual sanitization.
Use cases
- Cleaning logs from failed agent function calls.
- Sanitizing raw LLM responses before piping them into a downstream database.
- Debugging structured output prompts during the prototyping phase.
How to install
Works the same in every agent - Claude, Cursor, Codex, Copilot and 20+ more.
- 1
Download the ZIP
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- 2
Unzip into your skills folder
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- 3
Ask your agent to use it
Restart the agent if it was already running. It picks the skill up automatically - no config needed.
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Click the path to copy it. Create the folder if it does not exist yet.
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