JSON output schema validator
Paste a JSON Schema and a model's output to see whether it passes, with the exact path of every error, plus checks for OpenAI strict structured outputs.
Free, no sign-up. Runs entirely in your browser: nothing you type is sent to AgentScout or any AI provider.
What it supports
The validator covers the JSON Schema keywords most used for structured outputs: type (including type lists for nullable fields), properties, required, additionalProperties, items, enum, const, anyOf, minLength/maxLength, minimum/maximum, minItems/maxItems, pattern and local $ref to #/$defs. Other keywords are listed as not checked. If the output has text or a ```json fence around the JSON, the JSON part is pulled out first. Need a schema? Make one with the tool schema builder.
FAQ
Why validate a model's JSON output?
Even with structured-output modes, models can return missing fields, wrong types or values outside an enum, especially without strict mode. Checking against your schema catches this before it breaks your app.
What does OpenAI strict mode need?
OpenAI's strict structured outputs require every object to set additionalProperties to false and to list all of its properties in required. Use a type list like ["string", "null"] for optional values.
Does it support the full JSON Schema spec?
No. It covers the keywords most used for structured outputs and lists any others in the schema as not checked.
Is my data uploaded?
No. Validation runs in your browser.
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