diff --git a/.gitignore b/.gitignore
index 103d90e7..6148f1e4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,6 +12,7 @@ __pycache__
 
 # dependencies
 node_modules
+package-lock.json
 
 # IDEs and editors
 /.idea
diff --git a/README.md b/README.md
index 4849358f..cc26a12d 100644
--- a/README.md
+++ b/README.md
@@ -107,6 +107,30 @@ The ElevenLabs Agents Widgets provide an easy way to embed AI agents into any we
 
 Learn how to embed the widget into your website [here](https://elevenlabs.io/docs/agents-platform/customization/widget).
 
+#### Dynamic Variables in Widgets
+
+You can pass dynamic variables to your agent through HTML attributes:
+
+```html
+<elevenlabs-convai-widget
+  agent-id="your-agent-id"
+  dynamic-variables='{"user_name":"John Doe","account_type":"premium"}'
+></elevenlabs-convai-widget>
+```
+
+To handle missing required variables, use the `expected-dynamic-variables` and `missing-dynamic-variable-default` attributes:
+
+```html
+<elevenlabs-convai-widget
+  agent-id="your-agent-id"
+  dynamic-variables='{"user_name":"John Doe","current_plan":"premium"}'
+  expected-dynamic-variables='["user_name","current_plan","previous_orders","support_history"]'
+  missing-dynamic-variable-default="null"
+></elevenlabs-convai-widget>
+```
+
+This automatically fills missing variables (like `previous_orders` and `support_history`) with `null`, preventing conversation failures when your agent's tools require variables you don't have.
+
 ### Agents CLI
 
 The ElevenLabs Agents CLI allows you to manage your agents as code, with features like version control, templates, and multi-environment deployments.
diff --git a/packages/client/README.md b/packages/client/README.md
index 4bfc8fc5..12b8a24b 100644
--- a/packages/client/README.md
+++ b/packages/client/README.md
@@ -235,6 +235,60 @@ const conversation = await Conversation.startSession({
 });
 ```
 
+#### Dynamic Variables
+
+Dynamic variables allow you to pass runtime data to your agent's tools. If your agent has tools configured with dynamic variable references, you can provide these variables during conversation initiation.
+
+**Basic usage:**
+
+```ts
+const conversation = await Conversation.startSession({
+  agentId: "<your-agent-id>",
+  dynamicVariables: {
+    user_name: "John Doe",
+    account_type: "premium",
+    session_id: "abc123",
+  },
+});
+```
+
+**Handling missing required variables:**
+
+If your agent's tools require dynamic variables that you don't always have values for, you can use `expectedDynamicVariables` and `missingDynamicVariableDefault` to automatically fill missing variables with default values:
+
+```ts
+const conversation = await Conversation.startSession({
+  agentId: "<your-agent-id>",
+
+  // Variables you have available
+  dynamicVariables: {
+    user_name: "John Doe",
+    current_plan: "premium",
+  },
+
+  // All variables your agent's tools expect
+  expectedDynamicVariables: [
+    "user_name",
+    "current_plan",
+    "previous_orders",    // Will be auto-filled
+    "support_history",    // Will be auto-filled
+    "preferences",        // Will be auto-filled
+  ],
+
+  // Default value for missing variables (defaults to null)
+  missingDynamicVariableDefault: null,
+});
+```
+
+This prevents conversation failures when tools require variables you don't have. Missing variables will be automatically filled with the specified default value.
+
+**Supported default values:**
+- `null` (default)
+- Empty string: `""`
+- Custom string: `"N/A"`
+- Number: `0`
+- Boolean: `false`
+
 #### User identification
 
 You can optionally pass a user ID to identify the user in the conversation. This can be your own customer identifier. This will be included in the conversation initiation data sent to the server:
diff --git a/packages/client/src/utils/BaseConnection.ts b/packages/client/src/utils/BaseConnection.ts
index 170bc7f8..d9441683 100644
--- a/packages/client/src/utils/BaseConnection.ts
+++ b/packages/client/src/utils/BaseConnection.ts
@@ -48,6 +48,43 @@ export type BaseSessionConfig = {
   };
   customLlmExtraBody?: unknown;
   dynamicVariables?: Record<string, string | number | boolean>;
+  /**
+   * List of dynamic variable names that your agent's tools expect.
+   * Any variables in this list that aren't provided in dynamicVariables will be
+   * automatically filled with the value specified in missingDynamicVariableDefault.
+   *
+   * This is useful when your agent has tools that require dynamic variables,
+   * but you don't always have values for all of them.
+   *
+   * @example
+   * {
+   *   expectedDynamicVariables: ['clients', 'matters', 'conversation_history'],
+   *   missingDynamicVariableDefault: null,
+   *   dynamicVariables: { clients: 'client data' }
+   *   // Will automatically add: matters: null, conversation_history: null
+   * }
+   */
+  expectedDynamicVariables?: string[];
+  /**
+   * Default value to use for missing dynamic variables when tools require them.
+   * This helps avoid errors when tools expect dynamic variables that aren't provided.
+   * Only used when expectedDynamicVariables is specified.
+   *
+   * @default null
+   *
+   * @example
+   * // Fill missing dynamic variables with null
+   * { missingDynamicVariableDefault: null }
+   *
+   * @example
+   * // Fill missing dynamic variables with empty string
+   * { missingDynamicVariableDefault: "" }
+   *
+   * @example
+   * // Fill missing dynamic variables with a custom value
+   * { missingDynamicVariableDefault: "N/A" }
+   */
+  missingDynamicVariableDefault?: string | number | boolean | null;
   useWakeLock?: boolean;
   connectionDelay?: DelayConfig;
   textOnly?: boolean;
diff --git a/packages/client/src/utils/overrides.ts b/packages/client/src/utils/overrides.ts
index bf1bb188..dabe67df 100644
--- a/packages/client/src/utils/overrides.ts
+++ b/packages/client/src/utils/overrides.ts
@@ -31,8 +31,33 @@ export function constructOverrides(
     overridesEvent.custom_llm_extra_body = config.customLlmExtraBody;
   }
 
-  if (config.dynamicVariables) {
-    overridesEvent.dynamic_variables = config.dynamicVariables;
+  // Handle dynamic variables with auto-filling of missing required variables
+  if (config.dynamicVariables || config.expectedDynamicVariables) {
+    const providedVariables = config.dynamicVariables || {};
+
+    // If expectedDynamicVariables is specified, fill in missing ones with default value
+    if (
+      config.expectedDynamicVariables &&
+      config.expectedDynamicVariables.length > 0
+    ) {
+      const defaultValue = config.missingDynamicVariableDefault ?? null;
+      const filledVariables: Record<string, string | number | boolean | null> =
+        { ...providedVariables };
+
+      // Add missing variables with default value
+      for (const varName of config.expectedDynamicVariables) {
+        if (!(varName in filledVariables)) {
+          filledVariables[varName] = defaultValue;
+        }
+      }
+
+      overridesEvent.dynamic_variables = filledVariables as Record<
+        string,
+        string | number | boolean
+      >;
+    } else {
+      overridesEvent.dynamic_variables = providedVariables;
+    }
   }
 
   if (config.userId) {
diff --git a/packages/convai-widget-core/src/contexts/session-config.tsx b/packages/convai-widget-core/src/contexts/session-config.tsx
index 9dbf911b..ecb0422b 100644
--- a/packages/convai-widget-core/src/contexts/session-config.tsx
+++ b/packages/convai-widget-core/src/contexts/session-config.tsx
@@ -59,6 +59,36 @@ export function SessionConfigProvider({
     return undefined;
   });
 
+  const expectedDynamicVariablesJSON = useAttribute("expected-dynamic-variables");
+  const expectedDynamicVariables = useComputed(() => {
+    if (expectedDynamicVariablesJSON.value) {
+      try {
+        return JSON.parse(expectedDynamicVariablesJSON.value) as string[];
+      } catch (e: any) {
+        console.error(
+          `[ConversationalAI] Cannot parse expected-dynamic-variables: ${e?.message}`
+        );
+      }
+    }
+
+    return undefined;
+  });
+
+  const missingDynamicVariableDefaultAttr = useAttribute("missing-dynamic-variable-default");
+  const missingDynamicVariableDefault = useComputed(() => {
+    if (missingDynamicVariableDefaultAttr.value) {
+      try {
+        // Try to parse as JSON first (for null, numbers, booleans)
+        return JSON.parse(missingDynamicVariableDefaultAttr.value);
+      } catch {
+        // If JSON parse fails, treat as string
+        return missingDynamicVariableDefaultAttr.value;
+      }
+    }
+
+    return null;
+  });
+
   const { webSocketUrl } = useServerLocation();
   const agentId = useAttribute("agent-id");
   const signedUrl = useAttribute("signed-url");
@@ -68,6 +98,8 @@ export function SessionConfigProvider({
     const isWebRTC = useWebRTCEnabled.value;
     const baseConfig = {
       dynamicVariables: dynamicVariables.value,
+      expectedDynamicVariables: expectedDynamicVariables.value,
+      missingDynamicVariableDefault: missingDynamicVariableDefault.value,
       overrides: overrides.value,
       connectionDelay: { default: 300 },
       textOnly: textOnly.value,
diff --git a/packages/convai-widget-core/src/types/attributes.ts b/packages/convai-widget-core/src/types/attributes.ts
index cc5bf04a..df2e2c3e 100644
--- a/packages/convai-widget-core/src/types/attributes.ts
+++ b/packages/convai-widget-core/src/types/attributes.ts
@@ -25,6 +25,8 @@ export const CustomAttributeList = [
   "server-location",
   "language",
   "dynamic-variables",
+  "expected-dynamic-variables",
+  "missing-dynamic-variable-default",
   "show-avatar-when-collapsed",
   "override-prompt",
   "override-first-message",
diff --git a/packages/react-native/README.md b/packages/react-native/README.md
index 9504b177..0205e055 100644
--- a/packages/react-native/README.md
+++ b/packages/react-native/README.md
@@ -102,6 +102,11 @@ Starts a new conversation session.
 - `config.agentId`: ElevenLabs agent ID, not needed if you provide a conversationToken.
 - `config.conversationToken`: Optional pre-generated token, used for private agents that require authentication via your ElevenLabs API key.
 - `config.userId`: You can optionally pass a user ID to identify the user in the conversation. This can be your own customer identifier. This will be included in the conversation initiation data sent to the server.
+- `config.dynamicVariables`: Optional key-value pairs to pass runtime data to your agent's tools.
+- `config.expectedDynamicVariables`: Optional array of variable names your agent expects. Any missing variables will be auto-filled.
+- `config.missingDynamicVariableDefault`: Default value for missing variables (defaults to `null`). Can be `null`, string, number, or boolean.
+
+**Basic example:**
 
 ```typescript
 await conversation.startSession({
@@ -109,6 +114,45 @@ await conversation.startSession({
 });
 ```
 
+**With dynamic variables:**
+
+```typescript
+await conversation.startSession({
+  agentId: "your-agent-id",
+  dynamicVariables: {
+    user_name: "John Doe",
+    account_type: "premium",
+  },
+});
+```
+
+**Auto-filling missing required variables:**
+
+If your agent's tools require dynamic variables you don't always have, use `expectedDynamicVariables` to prevent errors:
+
+```typescript
+await conversation.startSession({
+  agentId: "your-agent-id",
+
+  // Variables you have
+  dynamicVariables: {
+    user_name: "John Doe",
+    current_plan: "premium",
+  },
+
+  // All variables your agent expects
+  expectedDynamicVariables: [
+    "user_name",
+    "current_plan",
+    "previous_orders",    // Will be auto-filled with null
+    "support_history",    // Will be auto-filled with null
+  ],
+
+  // Optional: customize the default value
+  missingDynamicVariableDefault: null, // Can also be "", "N/A", 0, false, etc.
+});
+```
+
 #### `endSession(): Promise<void>`
 
 Ends the current conversation session.
diff --git a/packages/react-native/src/ElevenLabsProvider.tsx b/packages/react-native/src/ElevenLabsProvider.tsx
index 9545ac01..b4b3fe8d 100644
--- a/packages/react-native/src/ElevenLabsProvider.tsx
+++ b/packages/react-native/src/ElevenLabsProvider.tsx
@@ -121,6 +121,8 @@ export const ElevenLabsProvider: React.FC<ElevenLabsProviderProps> = ({ children
     overrides,
     customLlmExtraBody,
     dynamicVariables,
+    expectedDynamicVariables,
+    missingDynamicVariableDefault,
     userId,
   } = useConversationSession(callbacksRef, setStatus, setConnect, setToken, setConversationId, tokenFetchUrl);
 
@@ -210,6 +212,8 @@ export const ElevenLabsProvider: React.FC<ElevenLabsProviderProps> = ({ children
       overrides,
       customLlmExtraBody,
       dynamicVariables,
+      expectedDynamicVariables,
+      missingDynamicVariableDefault,
       userId,
     });
 
@@ -223,7 +227,7 @@ export const ElevenLabsProvider: React.FC<ElevenLabsProviderProps> = ({ children
         callbacksRef.current.onError?.(error as string);
       }
     }
-  }, [handleParticipantReady, overrides, customLlmExtraBody, dynamicVariables, userId, callbacksRef]);
+  }, [handleParticipantReady, overrides, customLlmExtraBody, dynamicVariables, expectedDynamicVariables, missingDynamicVariableDefault, userId, callbacksRef]);
 
   const conversation: Conversation = {
     startSession,
diff --git a/packages/react-native/src/hooks/useConversationSession.ts b/packages/react-native/src/hooks/useConversationSession.ts
index 9cc82a5d..31134736 100644
--- a/packages/react-native/src/hooks/useConversationSession.ts
+++ b/packages/react-native/src/hooks/useConversationSession.ts
@@ -25,6 +25,10 @@ export const useConversationSession = (
   const [dynamicVariables, setDynamicVariables] = useState<
     ConversationConfig["dynamicVariables"]
   >({});
+  const [expectedDynamicVariables, setExpectedDynamicVariables] =
+    useState<ConversationConfig["expectedDynamicVariables"]>(undefined);
+  const [missingDynamicVariableDefault, setMissingDynamicVariableDefault] =
+    useState<ConversationConfig["missingDynamicVariableDefault"]>(null);
   const [userId, setUserId] = useState<ConversationConfig["userId"]>(undefined);
 
   const startSession = useCallback(
@@ -36,6 +40,10 @@ export const useConversationSession = (
         setOverrides(config.overrides || {});
         setCustomLlmExtraBody(config.customLlmExtraBody || null);
         setDynamicVariables(config.dynamicVariables || {});
+        setExpectedDynamicVariables(config.expectedDynamicVariables);
+        setMissingDynamicVariableDefault(
+          config.missingDynamicVariableDefault ?? null
+        );
         setUserId(config.userId);
 
         let conversationToken: string;
@@ -91,6 +99,8 @@ export const useConversationSession = (
         setOverrides({});
         setCustomLlmExtraBody(null);
         setDynamicVariables({});
+        setExpectedDynamicVariables(undefined);
+        setMissingDynamicVariableDefault(null);
         setUserId(undefined);
         setConversationId("");
 
@@ -110,6 +120,8 @@ export const useConversationSession = (
     overrides,
     customLlmExtraBody,
     dynamicVariables,
+    expectedDynamicVariables,
+    missingDynamicVariableDefault,
     userId,
   };
 };
diff --git a/packages/react-native/src/types.ts b/packages/react-native/src/types.ts
index 410d3b0d..eca0ae4c 100644
--- a/packages/react-native/src/types.ts
+++ b/packages/react-native/src/types.ts
@@ -81,6 +81,43 @@ export type ConversationConfig = {
   };
   customLlmExtraBody?: unknown;
   dynamicVariables?: Record<string, string | number | boolean>;
+  /**
+   * List of dynamic variable names that your agent's tools expect.
+   * Any variables in this list that aren't provided in dynamicVariables will be
+   * automatically filled with the value specified in missingDynamicVariableDefault.
+   *
+   * This is useful when your agent has tools that require dynamic variables,
+   * but you don't always have values for all of them.
+   *
+   * @example
+   * {
+   *   expectedDynamicVariables: ['clients', 'matters', 'conversation_history'],
+   *   missingDynamicVariableDefault: null,
+   *   dynamicVariables: { clients: 'client data' }
+   *   // Will automatically add: matters: null, conversation_history: null
+   * }
+   */
+  expectedDynamicVariables?: string[];
+  /**
+   * Default value to use for missing dynamic variables when tools require them.
+   * This helps avoid errors when tools expect dynamic variables that aren't provided.
+   * Only used when expectedDynamicVariables is specified.
+   *
+   * @default null
+   *
+   * @example
+   * // Fill missing dynamic variables with null
+   * { missingDynamicVariableDefault: null }
+   *
+   * @example
+   * // Fill missing dynamic variables with empty string
+   * { missingDynamicVariableDefault: "" }
+   *
+   * @example
+   * // Fill missing dynamic variables with a custom value
+   * { missingDynamicVariableDefault: "N/A" }
+   */
+  missingDynamicVariableDefault?: string | number | boolean | null;
   userId?: string;
 };
 
diff --git a/packages/react-native/src/utils/overrides.ts b/packages/react-native/src/utils/overrides.ts
index c1adcce1..d23f0736 100644
--- a/packages/react-native/src/utils/overrides.ts
+++ b/packages/react-native/src/utils/overrides.ts
@@ -33,8 +33,33 @@ export function constructOverrides(
     overridesEvent.custom_llm_extra_body = config.customLlmExtraBody;
   }
 
-  if (config.dynamicVariables) {
-    overridesEvent.dynamic_variables = config.dynamicVariables;
+  // Handle dynamic variables with auto-filling of missing required variables
+  if (config.dynamicVariables || config.expectedDynamicVariables) {
+    const providedVariables = config.dynamicVariables || {};
+
+    // If expectedDynamicVariables is specified, fill in missing ones with default value
+    if (
+      config.expectedDynamicVariables &&
+      config.expectedDynamicVariables.length > 0
+    ) {
+      const defaultValue = config.missingDynamicVariableDefault ?? null;
+      const filledVariables: Record<string, string | number | boolean | null> =
+        { ...providedVariables };
+
+      // Add missing variables with default value
+      for (const varName of config.expectedDynamicVariables) {
+        if (!(varName in filledVariables)) {
+          filledVariables[varName] = defaultValue;
+        }
+      }
+
+      overridesEvent.dynamic_variables = filledVariables as Record<
+        string,
+        string | number | boolean
+      >;
+    } else {
+      overridesEvent.dynamic_variables = providedVariables;
+    }
   }
 
   if (config.userId) {
diff --git a/packages/react/README.md b/packages/react/README.md
index 195cf4e2..d0c7829d 100644
--- a/packages/react/README.md
+++ b/packages/react/README.md
@@ -128,6 +128,60 @@ const conversation = useConversation({
 });
 ```
 
+#### Dynamic Variables
+
+Dynamic variables allow you to pass runtime data to your agent's tools. If your agent has tools configured with dynamic variable references, you can provide these variables during conversation initiation.
+
+**Basic usage:**
+
+```ts
+const conversationId = await conversation.startSession({
+  agentId: "<your-agent-id>",
+  dynamicVariables: {
+    user_name: "John Doe",
+    account_type: "premium",
+    session_id: "abc123",
+  },
+});
+```
+
+**Handling missing required variables:**
+
+If your agent's tools require dynamic variables that you don't always have values for, you can use `expectedDynamicVariables` and `missingDynamicVariableDefault` to automatically fill missing variables with default values:
+
+```ts
+const conversationId = await conversation.startSession({
+  agentId: "<your-agent-id>",
+
+  // Variables you have available
+  dynamicVariables: {
+    user_name: "John Doe",
+    current_plan: "premium",
+  },
+
+  // All variables your agent's tools expect
+  expectedDynamicVariables: [
+    "user_name",
+    "current_plan",
+    "previous_orders",    // Will be auto-filled
+    "support_history",    // Will be auto-filled
+    "preferences",        // Will be auto-filled
+  ],
+
+  // Default value for missing variables (defaults to null)
+  missingDynamicVariableDefault: null,
+});
+```
+
+This prevents conversation failures when tools require variables you don't have. Missing variables will be automatically filled with the specified default value.
+
+**Supported default values:**
+- `null` (default)
+- Empty string: `""`
+- Custom string: `"N/A"`
+- Number: `0`
+- Boolean: `false`
+
 #### User identification
 
 You can optionally pass a user ID to identify the user in the conversation. This can be your own customer identifier. This will be included in the conversation initiation data sent to the server: