Add docs for variables and overrides on assistants (#68)

- Add docs to add template variables and how to override them

Author: edwinzhng

assistants/persistent-assistants.mdx

@@ -14,3 +14,34 @@ The `/assistant` endpoint is there for convenience to save you creating your own
 </Accordion>
 
 Otherwise, you can just specify the assistant configuration when starting a call.
+
+## Variables
+
+Prompts, messages, and other assistant properties can be dynamically set when starting a call based on templates.
+These templates are defined using double curly braces `{{variableName}}`.
+This is useful when you want to customize the assistant for a specific call.
+
+For example, you could set the assistant's first message to "Hello, `{{name}}`!" and then set `name` to `John` when starting the call
+by passing `assistantOverrides` with `variableValues` to the API or SDK:
+
+```json
+{
+  "variableValues": {
+    "name": "John"
+  }
+}
+```
+
+#### Default variables
+
+By default, the following variables are automatically filled based on the current (UTC) time,
+meaning that you don't need to set them manually in `variableValues`:
+
+| Variable    | Description                    | Example              |
+| ----------- | ------------------------------ | -------------------- |
+| `{{now}}`   | Current date and time (UTC)    | Jan 1, 2024 12:00 PM |
+| `{{date}}`  | Current date (UTC)             | Jan 1, 2024          |
+| `{{time}}`  | Current time (UTC)             | 12:00 PM             |
+| `{{month}}` | Current month (UTC)            | January              |
+| `{{day}}`   | Current day of month (UTC)     | 1                    |
+| `{{year}}`  | Current year (UTC)             | 2024                 |

quickstart/web.mdx

@@ -130,7 +130,7 @@ vapi.start(assistantOptions);
 
 More configuration options can be found in the [Assistant](/api-reference/assistants/create-assistant) API reference.
 
-### Option 2: Persistant Assistant
+### Option 2: Persistent Assistant
 
 If you want to create an assistant that you can reuse across multiple calls, you can create a persistent assistant in the [Vapi Dashboard](https://dashboard.vapi.ai). Here's how you can do that:
 
@@ -144,8 +144,28 @@ Then, you can copy the assistant's ID at the top of the assistant detail page:
   <img src="/static/images/quickstart/assistant-id-dashboard.png" />
 </Frame>
 
-Now we can call `.start()`, passing the persistant assistant's ID:
+Now we can call `.start()`, passing the persistent assistant's ID:
 
 ```javascript
 vapi.start("79f3XXXX-XXXX-XXXX-XXXX-XXXXXXXXce48");
 ```
+
+If you need to override any assistant settings or set template variables, you can pass `assistantOverrides` as the second argument.
+
+For example, if the first message is "Hello `{{name}}`", you can set `assistantOverrides` to replace `{{name}}` with `John`:
+
+```javascript
+const assistantOverrides = {
+  transcriber: {
+    provider: "deepgram",
+    model: "nova-2",
+    language: "en-US",
+  },
+  recordingEnabled: false,
+  variableValues: {
+    name: "John",
+  },
+};
+
+vapi.start("79f3XXXX-XXXX-XXXX-XXXX-XXXXXXXXce48", assistantOverrides);
+```

sdk/web.mdx

@@ -70,6 +70,28 @@ vapi.start({
 });
 ```
 
+#### Overriding Assistant Configurations
+
+To override assistant settings or set template variables, you can pass `assistantOverrides` as the second argument.
+
+For example, if the first message is "Hello `{{name}}`", set `assistantOverrides` to the following to replace `{{name}}` with `John`:
+
+```javascript
+const assistantOverrides = {
+  transcriber: {
+    provider: "deepgram",
+    model: "nova-2",
+    language: "en-US",
+  },
+  recordingEnabled: false,
+  variableValues: {
+    name: "Alice",
+  },
+};
+
+vapi.start("79f3XXXX-XXXX-XXXX-XXXX-XXXXXXXXce48", assistantOverrides);
+```
+
 ### `.send()`
 
 During the call, you can send intermediate messages to the assistant (like [background messages](/assistants/background-messages)).