Schema Enforcement

Schema Enforcement ensures your LLM outputs conform to a defined JSON schema. Perf validates responses, auto-repairs common issues, applies semantic corrections (like fixing negative prices), and guarantees you receive properly structured data.

Why Schema Enforcement?

LLMs are unreliable at producing consistent JSON:

Missing required fields
Wrong data types (string instead of number)
Extra fields not in schema
Malformed JSON syntax
Markdown code blocks wrapping JSON

Perf’s Schema Enforcement:

Validates outputs against your JSON Schema
Auto-repairs common issues (type coercion, format fixes)
Semantic correction fixes domain-specific errors (negative prices, invalid ratings)
Retries with better prompts if validation fails
Guarantees schema-compliant responses

Using Schemas in Requests

Inline Schema

Pass a JSON Schema directly in your request:

curl -X POST https://api.withperf.pro/v1/chat \
  -H "Authorization: Bearer pk_live_abc123" \
  -H "Content-Type: application/json" \
  -d '{
    "messages": [
      {
        "role": "user",
        "content": "Extract contact info: John Smith, john@example.com, 555-1234"
      }
    ],
    "schema": {
      "type": "object",
      "properties": {
        "name": { "type": "string" },
        "email": { "type": "string", "format": "email" },
        "phone": { "type": "string" }
      },
      "required": ["name", "email"]
    }
  }'

Schema by ID

Reference a saved schema by ID or slug:

curl -X POST https://api.withperf.pro/v1/chat \
  -H "Authorization: Bearer pk_live_abc123" \
  -H "Content-Type: application/json" \
  -d '{
    "messages": [{"role": "user", "content": "Extract contact info..."}],
    "schema_id": "contact-extraction"
  }'

Project Default Schema

Set a default schema for your project in the Dashboard. All requests without an explicit schema will use it.

Schema Parameters

Parameter	Type	Description
`schema`	object	Inline JSON Schema (Draft 2020-12)
`schema_id`	string	ID or slug of a saved schema
`schema_strict`	boolean	Disable auto-repair, fail on any mismatch (default: `false`)

Response

When schema enforcement is active, responses include validation metadata:

{
  "choices": [{
    "message": {
      "content": "{\"name\": \"John Smith\", \"email\": \"john@example.com\", \"phone\": \"555-1234\"}"
    }
  }],
  "perf": {
    "schema_validation": {
      "enabled": true,
      "passed": true,
      "repaired": false,
      "schema_source": "inline"
    }
  }
}

Validation Fields

Field	Type	Description
`enabled`	boolean	Schema validation was active
`passed`	boolean	Final output passed validation
`repaired`	boolean	Auto-repair was applied
`schema_source`	string	`inline`, `schema_id`, or `project_default`

Auto-Repair

When schema_strict: false (default), Perf attempts to repair common issues:

Issue	Repair Action
String instead of number	Parse to number (`"42"` → `42`)
Number instead of string	Convert to string (`42` → `"42"`)
String instead of boolean	Parse (`"true"` → `true`)
Markdown code blocks	Extract JSON from `json ...`
Extra whitespace	Trim and normalize
Missing optional fields	Leave as undefined

Example: Auto-Repair in Action

LLM returns:

Here's the extracted data:
```json
{"name": "John", "age": "25"}

With schema requiring `age` as number, Perf:
1. Extracts JSON from markdown
2. Coerces `"25"` → `25`
3. Returns valid JSON

## Semantic Validation

Go beyond structural validation with semantic type hints. Add `x-semantic-type` to your schema fields to auto-correct common LLM errors like negative prices, out-of-range ratings, and invalid dates.

### Using x-semantic-type

```json
{
  "type": "object",
  "properties": {
    "price": {
      "type": "number",
      "x-semantic-type": "currency_positive"
    },
    "rating": {
      "type": "number",
      "x-semantic-type": "rating_1_5"
    },
    "customer_age": {
      "type": "integer",
      "x-semantic-type": "human_age"
    }
  }
}

Supported Semantic Types

Type	Description	Auto-Correction
`currency_positive`	Prices, amounts (must be positive)	`-$999` → `$999`
`currency_allow_negative`	Values that can be negative	Validates magnitude only
`human_age`	Person ages (0-130)	Clamps to valid range
`percentage`	Percentages (0-100 or 0-1)	Normalizes scale
`rating_1_5`	5-star ratings	`12` → `5` (clamps to max)
`rating_1_10`	10-point ratings	Clamps to 1-10 range
`email`	Email addresses	Format validation
`url`	URLs	Format validation
`date_past`	Historical dates	Flags future dates
`date_future`	Upcoming dates	Flags past dates

Example: Semantic Correction in Action

Request with semantic types:

curl -X POST https://api.withperf.pro/v1/chat \
  -H "Authorization: Bearer pk_live_abc123" \
  -H "Content-Type: application/json" \
  -d '{
    "messages": [{
      "role": "user",
      "content": "Extract: iPhone 15 Pro costs -$999, rating 12/5 stars"
    }],
    "response_format": {
      "type": "json_schema",
      "json_schema": {
        "name": "product",
        "schema": {
          "type": "object",
          "properties": {
            "name": { "type": "string" },
            "price": { "type": "number", "x-semantic-type": "currency_positive" },
            "rating": { "type": "number", "x-semantic-type": "rating_1_5" }
          },
          "required": ["name", "price", "rating"]
        }
      }
    }
  }'

Response with corrections:

{
  "choices": [{
    "message": {
      "content": "{\"name\": \"iPhone 15 Pro\", \"price\": 999, \"rating\": 5}"
    }
  }],
  "perf": {
    "semantic_validation": {
      "result": "corrected",
      "corrections": [
        {
          "field": "price",
          "original": -999,
          "corrected": 999,
          "reason": "currency_positive values must be non-negative",
          "confidence": 1.0
        },
        {
          "field": "rating",
          "original": 12,
          "corrected": 5,
          "reason": "rating_1_5 clamped to maximum value",
          "confidence": 1.0
        }
      ],
      "latency_ms": 3.2
    }
  }
}

Semantic Validation Response Fields

Field	Type	Description
`result`	string	`pass`, `corrected`, or `failed`
`corrections`	array	List of auto-corrections applied
`warnings`	array	Non-blocking issues detected
`latency_ms`	number	Validation latency in milliseconds

Strict Mode

Enable strict mode to disable auto-repair:

{
  "messages": [...],
  "schema": {...},
  "schema_strict": true
}

In strict mode:

No type coercion
No format repairs
Validation fails on any mismatch
Returns error if validation fails after retries

Managing Schemas

Create Schema (Dashboard API)

curl -X POST https://api.withperf.pro/v1/dashboard/projects/{projectId}/schemas \
  -H "Authorization: Bearer <clerk_jwt>" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Contact Extraction",
    "slug": "contact-extraction",
    "description": "Schema for extracting contact information",
    "schema": {
      "type": "object",
      "properties": {
        "name": { "type": "string" },
        "email": { "type": "string", "format": "email" },
        "phone": { "type": "string" }
      },
      "required": ["name", "email"]
    },
    "is_default": false
  }'

List Schemas

curl https://api.withperf.pro/v1/dashboard/projects/{projectId}/schemas \
  -H "Authorization: Bearer <clerk_jwt>"

Test Schema

Test a schema against sample data:

curl -X POST https://api.withperf.pro/v1/dashboard/projects/{projectId}/schemas/test \
  -H "Authorization: Bearer <clerk_jwt>" \
  -H "Content-Type: application/json" \
  -d '{
    "schema": {
      "type": "object",
      "properties": {
        "name": { "type": "string" }
      },
      "required": ["name"]
    },
    "data": {"name": "John"}
  }'

Supported JSON Schema Features

Perf supports JSON Schema Draft 2020-12 with these features:

Types

string, number, integer, boolean, null
object, array

String Formats

email, uri, date, date-time, uuid

Validation Keywords

required, properties, additionalProperties
minLength, maxLength, pattern
minimum, maximum, exclusiveMinimum, exclusiveMaximum
minItems, maxItems, uniqueItems
enum, const

Composition

allOf, anyOf, oneOf
$ref (local references only)

Best Practices

1. Keep Schemas Simple

{
  "type": "object",
  "properties": {
    "sentiment": { "enum": ["positive", "negative", "neutral"] },
    "confidence": { "type": "number", "minimum": 0, "maximum": 1 }
  },
  "required": ["sentiment", "confidence"]
}

2. Use Descriptive Names

Add title and description to help the LLM understand:

{
  "type": "object",
  "title": "Product Review Analysis",
  "properties": {
    "rating": {
      "type": "integer",
      "minimum": 1,
      "maximum": 5,
      "description": "Star rating from 1-5"
    }
  }
}

3. Prefer Enums for Categories

{
  "category": {
    "type": "string",
    "enum": ["bug", "feature", "question", "documentation"]
  }
}

4. Set Reasonable Defaults

Use default for optional fields:

{
  "properties": {
    "priority": {
      "type": "string",
      "enum": ["low", "medium", "high"],
      "default": "medium"
    }
  }
}

Error Handling

Validation Failed

If validation fails after retries:

{
  "error": {
    "type": "schema_validation_failed",
    "message": "Output failed schema validation after 2 attempts",
    "details": {
      "errors": [
        { "path": "/email", "message": "must match format \"email\"" }
      ]
    }
  }
}

Invalid Schema

If your schema is invalid:

{
  "error": {
    "type": "invalid_schema",
    "message": "Schema validation error: 'type' must be a string"
  }
}

Plan Limits

Tier	Max Schemas	Auto-Repair	Semantic Validation
Starter	3	No	No
Pro	10	Yes	Yes
Growth	50	Yes	Yes
Enterprise	Unlimited	Yes	Yes

Chat API - Use schemas with chat completions
Streaming API - Schema validation with streaming
Logs API - View validation history

Getting Started

Voice Agents

SDKs

API Documentation

Platform

Advanced

Resources

​Schema Enforcement

​Why Schema Enforcement?

​Using Schemas in Requests

​Inline Schema

​Schema by ID

​Project Default Schema

​Schema Parameters

​Response

​Validation Fields

​Auto-Repair

​Example: Auto-Repair in Action

​Supported Semantic Types

​Example: Semantic Correction in Action

​Semantic Validation Response Fields

​Strict Mode

​Managing Schemas

​Create Schema (Dashboard API)

​List Schemas

​Test Schema

​Supported JSON Schema Features

​Types

​String Formats

​Validation Keywords

​Composition

​Best Practices

​1. Keep Schemas Simple

​2. Use Descriptive Names

​3. Prefer Enums for Categories

​4. Set Reasonable Defaults

​Error Handling

​Validation Failed

​Invalid Schema

​Plan Limits

​Related Endpoints