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Model Inference uses JSON Schema to define the structure of responses. This reference documents supported features and patterns.

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Supported draft version

Model Inference supports JSON Schema Draft 2020-12 features commonly used for structured output definition.

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Basic types

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String

{
  "type": "string"
}
With constraints: 
{
  "type": "string",
  "minLength": 1,
  "maxLength": 1000
}

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Number

{
  "type": "number"
}
With constraints: 
{
  "type": "number",
  "minimum": 0,
  "maximum": 1
}

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Integer

{
  "type": "integer",
  "minimum": 0
}

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Boolean

{
  "type": "boolean"
}

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Null

{
  "type": "null"
}

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Object type

Define structured objects with named properties: 
{
  "type": "object",
  "properties": {
    "name": { "type": "string" },
    "age": { "type": "integer" },
    "active": { "type": "boolean" }
  },
  "required": ["name", "age"]
}

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Required properties

Use the required array to specify mandatory fields: 
{
  "type": "object",
  "properties": {
    "id": { "type": "string" },
    "title": { "type": "string" },
    "description": { "type": "string" }
  },
  "required": ["id", "title"]
}

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Additional properties

Control whether extra properties are allowed: 
{
  "type": "object",
  "properties": {
    "name": { "type": "string" }
  },
  "additionalProperties": false
}

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Array type

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Simple arrays

{
  "type": "array",
  "items": { "type": "string" }
}

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Array constraints

{
  "type": "array",
  "items": { "type": "string" },
  "minItems": 1,
  "maxItems": 10
}

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Arrays of objects

{
  "type": "array",
  "items": {
    "type": "object",
    "properties": {
      "name": { "type": "string" },
      "value": { "type": "number" }
    },
    "required": ["name", "value"]
  }
}

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Enum constraint

Restrict values to a predefined set: 
{
  "type": "string",
  "enum": ["low", "medium", "high"]
}
Enum with numbers: 
{
  "type": "integer",
  "enum": [1, 2, 3, 4, 5]
}

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Numeric constraints

KeywordDescription
minimumValue must be >= this number
maximumValue must be <= this number
exclusiveMinimumValue must be > this number
exclusiveMaximumValue must be < this number
multipleOfValue must be divisible by this number
Example: 
{
  "type": "number",
  "minimum": 0,
  "maximum": 100,
  "multipleOf": 0.01
}

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String constraints

KeywordDescription
minLengthMinimum string length
maxLengthMaximum string length
patternRegex pattern the string must match
Example: 
{
  "type": "string",
  "minLength": 1,
  "maxLength": 500,
  "pattern": "^[A-Z][a-z]+$"
}

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Array constraints

KeywordDescription
minItemsMinimum array length
maxItemsMaximum array length
uniqueItemsAll items must be unique
Example: 
{
  "type": "array",
  "items": { "type": "string" },
  "minItems": 1,
  "maxItems": 5,
  "uniqueItems": true
}

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Descriptions

Add descriptions to help the model understand field purpose: 
{
  "type": "object",
  "properties": {
    "sentiment": {
      "type": "string",
      "enum": ["positive", "negative", "neutral"],
      "description": "The overall emotional tone of the text"
    },
    "confidence": {
      "type": "number",
      "minimum": 0,
      "maximum": 1,
      "description": "Confidence score where 0 is uncertain and 1 is certain"
    }
  },
  "required": ["sentiment", "confidence"]
}

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Nested structures

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Nested objects

{
  "type": "object",
  "properties": {
    "metadata": {
      "type": "object",
      "properties": {
        "created_at": { "type": "string" },
        "version": { "type": "integer" }
      },
      "required": ["created_at"]
    },
    "data": {
      "type": "object",
      "properties": {
        "items": {
          "type": "array",
          "items": { "type": "string" }
        }
      }
    }
  },
  "required": ["metadata"]
}

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Common patterns

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Classification result

{
  "type": "object",
  "properties": {
    "category": {
      "type": "string",
      "enum": ["A", "B", "C", "D"]
    },
    "confidence": {
      "type": "number",
      "minimum": 0,
      "maximum": 1
    },
    "reasoning": {
      "type": "string"
    }
  },
  "required": ["category", "confidence"]
}

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Entity extraction

{
  "type": "object",
  "properties": {
    "entities": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "text": { "type": "string" },
          "type": {
            "type": "string",
            "enum": ["person", "organization", "location", "date"]
          },
          "start_index": { "type": "integer" },
          "end_index": { "type": "integer" }
        },
        "required": ["text", "type"]
      }
    }
  },
  "required": ["entities"]
}

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Summary with key points

{
  "type": "object",
  "properties": {
    "summary": {
      "type": "string",
      "maxLength": 500
    },
    "key_points": {
      "type": "array",
      "items": { "type": "string" },
      "minItems": 1,
      "maxItems": 5
    },
    "word_count": {
      "type": "integer",
      "minimum": 0
    }
  },
  "required": ["summary", "key_points"]
}

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CRON expression result

{
  "type": "object",
  "properties": {
    "cron_expression": {
      "type": "string",
      "pattern": "^[\\d\\*\\/\\-\\,]+\\s+[\\d\\*\\/\\-\\,]+\\s+[\\d\\*\\/\\-\\,\\?LW]+\\s+[\\d\\*\\/\\-\\,]+\\s+[\\d\\*\\/\\-\\,\\?L#]+$",
      "description": "Valid CRON expression"
    },
    "human_readable": {
      "type": "string",
      "description": "Human-readable description of the schedule"
    },
    "next_runs": {
      "type": "array",
      "items": { "type": "string" },
      "maxItems": 3,
      "description": "Next 3 scheduled execution times in ISO format"
    }
  },
  "required": ["cron_expression", "human_readable"]
}

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TypeScript mapping

JSON Schema TypeTypeScript Type
stringstring
numbernumber
integernumber
booleanboolean
nullnull
arrayT[]
object{ [key: string]: T }
enumUnion type ('a' | 'b' | 'c')

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