OpenAI API Tool Parameters JSON Schema

openai-api-tool-parameters.schema.json

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://example.com/schemas/openai-api-tool-parameters.schema.json",
  "title": "OpenAI Chat Completions — Parameters (Supported JSON Schema Subset)",
  "description": "Meta‑schema for validating a tool function's `parameters` object against the subset of JSON Schema supported by OpenAI Structured Outputs and function calling. See: https://platform.openai.com/docs/guides/structured-outputs#supported-schemas",

  "type": "object",
  "allOf": [
    { "$ref": "#/$defs/ObjectRoot" }
  ],

  "$defs": {
    "SchemaNode": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "title": { "type": "string" },
        "description": { "type": "string" },

        "type": {
          "oneOf": [
            { "enum": ["object", "array", "string", "number", "integer", "boolean", "null"] },
            {
              "type": "array",
              "minItems": 1,
              "uniqueItems": true,
              "items": { "enum": ["object", "array", "string", "number", "integer", "boolean", "null"] }
            }
          ]
        },

        "const": { "type": ["string", "number", "integer", "boolean", "null"] },
        "enum": {
          "type": "array",
          "minItems": 1,
          "uniqueItems": true,
          "items": { "type": ["string", "number", "integer", "boolean", "null"] }
        },

        "$ref": { "type": "string" },
        "$defs": {
          "type": "object",
          "additionalProperties": { "$ref": "#/$defs/SchemaNode" }
        },

        "anyOf": {
          "type": "array",
          "minItems": 1,
          "items": { "$ref": "#/$defs/SchemaNode" }
        },

        "properties": {
          "type": "object",
          "additionalProperties": { "$ref": "#/$defs/SchemaNode" }
        },

        "required": {
          "type": "array",
          "items": { "type": "string" },
          "uniqueItems": true
        },

        "additionalProperties": { "const": false },

        "items": { "$ref": "#/$defs/SchemaNode" },

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

        "pattern": { "type": "string" },
        "format": {
          "type": "string",
          "enum": [
            "date-time",
            "time",
            "date",
            "duration",
            "email",
            "hostname",
            "ipv4",
            "ipv6",
            "uuid"
          ]
        },

        "multipleOf": { "type": "number", "exclusiveMinimum": 0 },
        "maximum": { "type": "number" },
        "exclusiveMaximum": { "type": "number" },
        "minimum": { "type": "number" },
        "exclusiveMinimum": { "type": "number" }
      },

      "allOf": [
        { "not": { "required": ["allOf"] } },
        { "not": { "required": ["oneOf"] } },
        { "not": { "required": ["not"] } },
        { "not": { "required": ["if"] } },
        { "not": { "required": ["then"] } },
        { "not": { "required": ["else"] } },
        { "not": { "required": ["dependentRequired"] } },
        { "not": { "required": ["dependentSchemas"] } },

        {
          "if": { "properties": { "type": { "const": "object" } }, "required": ["type"] },
          "then": { "required": ["additionalProperties"] }
        },
        {
          "if": {
            "properties": { "type": { "type": "array", "contains": { "const": "object" } } },
            "required": ["type"]
          },
          "then": { "required": ["additionalProperties"] }
        },

        { "if": { "required": ["properties"] }, "then": { "required": ["required"] } },

        { "not": { "properties": { "items": { "type": "array" } }, "required": ["items"] } }
      ]
    },

    "ObjectRoot": {
      "allOf": [
        { "$ref": "#/$defs/SchemaNode" },
        { "properties": { "type": { "const": "object" } }, "required": ["type"], "$comment": "Root must be an object schema because tool arguments are an object; top-level anyOf is not allowed." },
        { "not": { "required": ["anyOf"] } }
      ]
    }
  }
}