Add support for Structured Outputs on OpenAI (#30)

Author: kevinmingtarja

src/models/openai/chat.ts

@@ -115,6 +115,9 @@ class OpenAIChatInput {
    *
    * If set to `ResponseFormat.Json`, the response will be a JSON object.
    *
+   * If set to `ResponseFormat.JsonSchema`, the response will be a JSON object
+   * that conforms to the provided JSON schema.
+   *
    * @default ResponseFormat.Text
    */
   @alias("response_format")
@@ -286,6 +289,8 @@ class OpenAIChatOutput {
   usage!: Usage;
 }
 
+type JsonSchemaFunction = (jsonSchema: string) => ResponseFormat;
+
 /**
  * An object specifying the format that the model must output.
  */
@@ -296,6 +301,13 @@ export class ResponseFormat {
    */
   readonly type!: string;
 
+  /**
+   * The JSON schema to use for the response format.
+   */
+  @omitnull()
+  @alias("json_schema")
+  readonly jsonSchema: JSON.Raw | null = null;
+
   /**
    * Instructs the model to output the response as a JSON object.
    *
@@ -307,6 +319,20 @@ export class ResponseFormat {
    */
   static Json: ResponseFormat = { type: "json_object" };
 
+  /**
+   * Enables Structured Outputs which guarantees the model will match your supplied JSON schema.
+   *
+   * See https://platform.openai.com/docs/guides/structured-outputs
+   */
+  static JsonSchema: JsonSchemaFunction = (
+    jsonSchema: string,
+  ): ResponseFormat => {
+    return {
+      type: "json_schema",
+      jsonSchema: jsonSchema,
+    };
+  };
+
   /**
    * Instructs the model to output the response as a plain text string.
    *
@@ -339,7 +365,7 @@ export class Tool {
   /**
    * The definition of the function.
    */
-  function: FunctionDefinition = new FunctionDefinition();
+  function!: FunctionDefinition;
 }
 
 /**
@@ -360,13 +386,30 @@ export class FunctionDefinition {
   @omitnull()
   description: string | null = null;
 
+  /**
+   * Whether to enable strict schema adherence when generating the function call.
+   * If set to true, the model will follow the exact schema defined in the parameters field.
+   *
+   * See https://platform.openai.com/docs/guides/function-calling
+   *
+   * @remarks
+   * In order to guarantee strict schema adherence, disable parallel function calls
+   * by setting {@link OpenAIChatInput.parallelToolCalls}=false.
+   *
+   * See https://platform.openai.com/docs/guides/function-calling/parallel-function-calling-and-structured-outputs
+   *
+   * @default false
+   */
+  @omitif("this.strict == false")
+  strict: bool = false;
+
   /**
    * The parameters the functions accepts, described as a JSON Schema object.
    *
    * See https://platform.openai.com/docs/guides/function-calling
    */
   @omitnull()
-  parameters: JSON.Raw | null = null; // TODO: verify this works
+  parameters: JSON.Raw | null = null;
 }
 
 /**
@@ -681,6 +724,11 @@ class CompletionMessage extends Message {
     super(role, content);
   }
 
+  /**
+   * The refusal message generated by the model.
+   */
+  refusal: string | null = null;
+
   /**
    * The tool calls generated by the model, such as function calls.
    */