> ## Documentation Index
> Fetch the complete documentation index at: https://docs.telli.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Variables
> Learn how to use variables to personalize your agent's prompts dynamically.
Variables allow you to **inject dynamic data directly into your agent's prompt**, like the customer's name, phone number, current date, or any custom data you define. This lets your agent personalize conversations and access relevant information without hardcoding it into the prompt.
## Quick Start
Use double curly braces: `{{variableName}}`
Variables like `{{firstName}}`, `{{currentDate}}`, and `{{phoneNumber}}` are always available
Add custom properties to contacts (e.g., `{{contractId}}`, `{{city}}`) and reference them in your prompt
***
* **Personalize greetings:** *"Hi `{{firstName}}`, this is Emma from Telli"*
* **Reference customer data:** *"I see you're calling about contract `{{contractId}}`"*
* **Context-aware routing:** Use customer properties to guide the conversation flow
* **Time-based behavior:** Adjust responses based on `{{currentTime}}` or `{{currentWeekday}}`
* **Pass order details:** Include order numbers, product names, or any custom data from your system
These are standard variables that telli provides automatically for every call. You don't need to configure them, they're always available:
| **Variable** | **Description** |
| :----------------------- | :-------------------------------------- |
| **`{{firstName}}`** | Customer's first name |
| **`{{lastName}}`** | Customer's last name |
| **`{{phoneNumber}}`** | Customer's phone number |
| **`{{email}}`** | Customer's email address |
| **`{{language}}`** | Customer's language |
| **`{{currentDate}}`** | Today's date |
| **`{{currentTime}}`** | Current time |
| **`{{currentWeekday}}`** | Current day of the week |
| **`{{callDirection}}`** | Whether the call is inbound or outbound |
Variables and properties you define yourself when creating contacts in telli. These give you complete flexibility to pass any information to any agent in the account.
| **Variable** | **Example Use Case** |
| :------------------------------ | :-------------------------------- |
| **`{{product}}`** | Customer's current product |
| **`{{city}}`** | Customer's city |
| **`{{customerId}}`** | Customer ID |
| **`{{contractId}}`** | Contract number |
| **`{{currentTotalPrice}}`** | Current contract value |
| **`{{__contact_empfangsart}}`** | Custom field from contact details |
The variable names you use in the prompt must exactly match the names you define in your contact details. If you name a field **`contractId`** in the contact, you must reference it as **`{{contractId}}`** in the prompt, not **`{{contract_id}}`** or **`{{ContractId}}`**.
***
**Define Variables in a Centralized Section**
**Define all variables in a centralized section** so the agent has full clarity on what values are available.
***
**Don't Build Logic Around Raw Values**
If a variable is unknown, empty, or **`0`**, the agent has no instruction on how to interpret it and may not know which path to follow.
Instead, clearly **define what each variable represents in natural language** and explicitly instruct the agent what to do in each scenario.
### What not to do
```
Before proceeding, review the available customer data and choose the path:
{{letter_received}} == "Yes" and {{rsv_present}} == "Yes" → Path 6.2
{{letter_received}} == "Yes" and {{rsv_present}} == "No" → Path 6.3
```
What the agent sees if there is no letter and no RSV:
`0 == "Yes" and 0 == "Yes" → Path 6.2`
The agent sees the raw template syntax and may not know what to do if a value is missing or unexpected.
### What to do
```
# Available customer data
- Letter received: {{letter_received}}
- Legal protection insurance (RSV): {{rsv_present}}
# Routing rules
- If the customer has received the letter AND has legal protection insurance → follow Path 6.2
- If the customer has received the letter but does NOT have legal protection insurance → follow Path 6.3
- If the letter status is unknown or empty → ask the customer whether they have received a letter before proceeding
```
This way the agent understands the meaning behind each variable and knows exactly what to do in every scenario, including when data is missing.
***
**Reference Variables Where They're Used**
For longer prompts, define the variable clearly in a centralized section at the top, then reference it again right before it's actually used. This helps reinforce context and reduces the risk of misapplication.
***
**Use Them in Workflows Too**
The contact properties you set up here also work in workflows. When a workflow runs after a call, you can use the same values to send a webhook, update a contact, or sync to your CRM. You only need to set them up once.
See [Workflows](/cookbooks/workflows/overview) for the full list of places they can show up.
* Variable names are **case-sensitive**. `{{contractId}}` is different from `{{ContractId}}`.
* System default variables are available on every call automatically
* Custom variables only populate if the contact has that property defined
* If a variable is undefined, the agent sees an empty value. Make sure to handle missing data in your prompt logic.
* Variables can be used anywhere in the prompt: in the identity section, conversation script, or rules
To avoid confusion, always test your prompt with both populated and empty variable values to ensure the agent handles all scenarios gracefully.