Template Syntax & Naming

Variable reference syntax and naming rules

Variable References

Use double curly braces in text fields:

{{variable_name}}

Valid Examples

"Hello {{customer_name}}, your appointment is at {{appointment_time}}"
"Your order #{{order_id}} will arrive on {{delivery_date}}"

Invalid Examples

{user_input}           ❌ Single braces
{{User Input}}         ❌ Spaces
{{user-input}}         ❌ Hyphens
{{userInput}}          ❌ camelCase not allowed
{{ user_input }}       ❌ Spaces inside braces

Template Validation

The system checks:

• Existence: Referenced variable exists
• Syntax: Valid {{name}} form
• Types: Value matches declared type where relevant
• Availability: Variable is available at the current node (flow agent)

Naming Conventions

All variables must follow these rules:

Rules

1. Format: snake_case only
2. Start: Lowercase letter (a–z)
3. Characters: Lowercase letters, digits, underscores
4. Length: 1–50 characters
5. Reserved: Do not reuse system variable names

Valid Examples

customer_name          ✅
appointment_date_1     ✅
user_phone_number      ✅
api_response_data      ✅
is_premium_user        ✅

Invalid Examples

customerName           ❌ camelCase
Customer_Name          ❌ Capital letters
customer-name          ❌ Hyphens
customer name          ❌ Spaces
123_customer           ❌ Starts with number
_customer_name         ❌ Starts with underscore
customer_name!         ❌ Special characters

See System Variables for reserved names and Validation for how errors are shown.

Jinja2 Template Syntax

Prompts support full Jinja2 template syntax beyond simple {{variable_name}} substitution. You can use conditionals, filters, and any standard Jinja2 expression:

{% if direction == "outbound" %}
Hi {{customer_name}}, I'm calling from Acme Corporation.
{% else %}
Thanks for calling! How can I help you today?
{% endif %}

Your balance is {{balance | default("unavailable")}}.

Templates are processed server-side — the LLM receives the rendered output, not the template. For the full syntax reference including all filters, tests, and operators, see the Jinja2 Template Designer Documentation.