diff --git a/.changeset/forty-bulldogs-shop.md b/.changeset/forty-bulldogs-shop.md
new file mode 100644
index 0000000..0f8729c
--- /dev/null
+++ b/.changeset/forty-bulldogs-shop.md
@@ -0,0 +1,6 @@
+---
+"@livekit/agents": minor  
+"@livekit/agents-plugin-openai": minor
+---
+
+OpenAI function calling: support arrays and optional fields in function call schema
diff --git a/agents/src/llm/function_context.test.ts b/agents/src/llm/function_context.test.ts
new file mode 100644
index 0000000..52a090f
--- /dev/null
+++ b/agents/src/llm/function_context.test.ts
@@ -0,0 +1,247 @@
+// SPDX-FileCopyrightText: 2024 LiveKit, Inc.
+//
+// SPDX-License-Identifier: Apache-2.0
+import { describe, expect, it } from 'vitest';
+import { z } from 'zod';
+import { CallableFunction, oaiParams } from './function_context.js';
+
+describe('function_context', () => {
+  describe('oaiParams', () => {
+    it('should handle basic object schema', () => {
+      const schema = z.object({
+        name: z.string().describe('The user name'),
+        age: z.number().describe('The user age'),
+      });
+
+      const result = oaiParams(schema);
+
+      expect(result).toEqual({
+        type: 'object',
+        properties: {
+          name: {
+            type: 'string',
+            description: 'The user name',
+          },
+          age: {
+            type: 'number',
+            description: 'The user age',
+          },
+        },
+        required: ['name', 'age'],
+      });
+    });
+
+    it('should handle enum fields', () => {
+      const schema = z.object({
+        color: z.enum(['red', 'blue', 'green']).describe('Choose a color'),
+      });
+
+      const result = oaiParams(schema);
+
+      expect(result).toEqual({
+        type: 'object',
+        properties: {
+          color: {
+            type: 'string',
+            description: 'Choose a color',
+            enum: ['red', 'blue', 'green'],
+          },
+        },
+        required: ['color'],
+      });
+    });
+
+    it('should handle array fields', () => {
+      const schema = z.object({
+        tags: z.array(z.string()).describe('List of tags'),
+      });
+
+      const result = oaiParams(schema);
+
+      expect(result).toEqual({
+        type: 'object',
+        properties: {
+          tags: {
+            type: 'array',
+            description: 'List of tags',
+            items: {
+              type: 'string',
+            },
+          },
+        },
+        required: ['tags'],
+      });
+    });
+
+    it('should handle array of enums', () => {
+      const schema = z.object({
+        colors: z.array(z.enum(['red', 'blue', 'green'])).describe('List of colors'),
+      });
+
+      const result = oaiParams(schema);
+
+      expect(result).toEqual({
+        type: 'object',
+        properties: {
+          colors: {
+            type: 'array',
+            description: 'List of colors',
+            items: {
+              type: 'string',
+              enum: ['red', 'blue', 'green'],
+            },
+          },
+        },
+        required: ['colors'],
+      });
+    });
+
+    it('should handle optional fields', () => {
+      const schema = z.object({
+        name: z.string().describe('The user name'),
+        age: z.number().optional().describe('The user age'),
+      });
+
+      const result = oaiParams(schema);
+
+      expect(result).toEqual({
+        type: 'object',
+        properties: {
+          name: {
+            type: 'string',
+            description: 'The user name',
+          },
+          age: {
+            type: 'number',
+            description: 'The user age',
+          },
+        },
+        required: ['name'], // age should not be required
+      });
+    });
+
+    it('should handle fields without descriptions', () => {
+      const schema = z.object({
+        name: z.string(),
+        age: z.number(),
+      });
+
+      const result = oaiParams(schema);
+
+      expect(result).toEqual({
+        type: 'object',
+        properties: {
+          name: {
+            type: 'string',
+            description: undefined,
+          },
+          age: {
+            type: 'number',
+            description: undefined,
+          },
+        },
+        required: ['name', 'age'],
+      });
+    });
+  });
+
+  describe('CallableFunction type', () => {
+    it('should properly type a callable function', async () => {
+      const schema = z.object({
+        name: z.string().describe('The user name'),
+        age: z.number().describe('The user age'),
+      });
+
+      const testFunction: CallableFunction<typeof schema, string> = {
+        description: 'Test function',
+        parameters: schema,
+        execute: async (args: z.infer<typeof schema>) => {
+          // TypeScript should recognize args.name and args.age
+          return `${args.name} is ${args.age} years old`;
+        },
+      };
+
+      const result = await testFunction.execute({ name: 'John', age: 30 });
+      expect(result).toBe('John is 30 years old');
+    });
+
+    it('should handle async execution', async () => {
+      const schema = z.object({
+        delay: z.number().describe('Delay in milliseconds'),
+      });
+
+      const testFunction: CallableFunction<typeof schema, number> = {
+        description: 'Async test function',
+        parameters: schema,
+        execute: async (args: z.infer<typeof schema>) => {
+          await new Promise((resolve) => setTimeout(resolve, args.delay));
+          return args.delay;
+        },
+      };
+
+      const start = Date.now();
+      const result = await testFunction.execute({ delay: 100 });
+      const duration = Date.now() - start;
+
+      expect(result).toBe(100);
+      expect(duration).toBeGreaterThanOrEqual(95); // Allow for small timing variations
+    });
+
+    describe('nested array support', () => {
+      it('should handle nested array fields', () => {
+        const schema = z.object({
+          items: z.array(
+            z.object({
+              name: z.string().describe('the item name'),
+              modifiers: z
+                .array(
+                  z.object({
+                    modifier_name: z.string(),
+                    modifier_value: z.string(),
+                  }),
+                )
+                .describe('list of the modifiers applied on this item, such as size'),
+            }),
+          ),
+        });
+        const result = oaiParams(schema);
+        expect(result).toEqual({
+          type: 'object',
+          properties: {
+            items: {
+              type: 'array',
+              description: undefined,
+              items: {
+                type: 'object',
+                properties: {
+                  name: {
+                    type: 'string',
+                    description: 'the item name',
+                  },
+                  modifiers: {
+                    type: 'array',
+                    description: 'list of the modifiers applied on this item, such as size',
+                    items: {
+                      type: 'object',
+                      properties: {
+                        modifier_name: {
+                          type: 'string',
+                        },
+                        modifier_value: {
+                          type: 'string',
+                        },
+                      },
+                      required: ['modifier_name', 'modifier_value'],
+                    },
+                  },
+                },
+                required: ['name', 'modifiers'],
+              },
+            },
+          },
+          required: ['items'],
+        });
+      });
+    });
+  });
+});
diff --git a/agents/src/llm/function_context.ts b/agents/src/llm/function_context.ts
index af193b7..864242a 100644
--- a/agents/src/llm/function_context.ts
+++ b/agents/src/llm/function_context.ts
@@ -34,29 +34,50 @@ export type FunctionContext = {
 /** @internal */
 export const oaiParams = (p: z.AnyZodObject) => {
   const properties: Record<string, any> = {};
-  const required_properties: string[] = [];
+  const requiredProperties: string[] = [];
 
-  for (const key in p.shape) {
-    const field = p.shape[key];
-    const description = field._def.description || undefined;
-    let type: string;
-    let enumValues: any[] | undefined;
+  const processZodType = (field: z.ZodTypeAny): any => {
+    const isOptional = field instanceof z.ZodOptional;
+    const nestedField = isOptional ? field._def.innerType : field;
+    const description = field._def.description;
 
-    if (field instanceof z.ZodEnum) {
-      enumValues = field._def.values;
-      type = typeof enumValues![0];
+    if (nestedField instanceof z.ZodEnum) {
+      return {
+        type: typeof nestedField._def.values[0],
+        ...(description && { description }),
+        enum: nestedField._def.values,
+      };
+    } else if (nestedField instanceof z.ZodArray) {
+      const elementType = nestedField._def.type;
+      return {
+        type: 'array',
+        ...(description && { description }),
+        items: processZodType(elementType),
+      };
+    } else if (nestedField instanceof z.ZodObject) {
+      const { properties, required } = oaiParams(nestedField);
+      return {
+        type: 'object',
+        ...(description && { description }),
+        properties,
+        required,
+      };
     } else {
-      type = field._def.typeName.toLowerCase();
+      let type = nestedField._def.typeName.toLowerCase();
+      type = type.includes('zod') ? type.substring(3) : type;
+      return {
+        type,
+        ...(description && { description }),
+      };
     }
+  };
 
-    properties[key] = {
-      type: type.includes('zod') ? type.substring(3) : type,
-      description,
-      enum: enumValues,
-    };
+  for (const key in p.shape) {
+    const field = p.shape[key];
+    properties[key] = processZodType(field);
 
-    if (!field._def.defaultValue) {
-      required_properties.push(key);
+    if (!(field instanceof z.ZodOptional)) {
+      requiredProperties.push(key);
     }
   }
 
@@ -64,6 +85,6 @@ export const oaiParams = (p: z.AnyZodObject) => {
   return {
     type,
     properties,
-    required_properties,
+    required: requiredProperties,
   };
 };
diff --git a/plugins/openai/src/realtime/api_proto.ts b/plugins/openai/src/realtime/api_proto.ts
index f23e93e..9596f80 100644
--- a/plugins/openai/src/realtime/api_proto.ts
+++ b/plugins/openai/src/realtime/api_proto.ts
@@ -79,7 +79,7 @@ export interface Tool {
         [prop: string]: any;
       };
     };
-    required_properties: string[];
+    required: string[];
   };
 }