Liquid Templating

Endprompt uses Liquid templating to create dynamic prompts. This lets you inject request data, apply transformations, and add conditional logic to your prompts.

Basic Syntax

Variable Output

Use double curly braces to output values:

{{ inputs.name }}
{{ inputs.text }}
{{ inputs.count }}

Filters

Apply filters to transform values:

{{ inputs.name | upcase }}
{{ inputs.text | truncate: 100 }}
{{ inputs.items | size }}

Accessing Input Values

All input fields are available under inputs:

Customer name: {{ inputs.customer_name }}
Order ID: {{ inputs.order_id }}
Items: {{ inputs.items | join: ", " }}

Default Values

Use the default filter for optional fields:

Language: {{ inputs.language | default: "English" }}
Max length: {{ inputs.max_length | default: 100 }}

Always provide defaults for optional fields to ensure your prompt works even when values aren’t provided.

Common Filters

String Filters

Filter	Description	Example
`upcase`	Convert to uppercase	`{{ "hello" \| upcase }}` → `HELLO`
`downcase`	Convert to lowercase	`{{ "HELLO" \| downcase }}` → `hello`
`capitalize`	Capitalize first letter	`{{ "hello" \| capitalize }}` → `Hello`
`truncate`	Shorten with ellipsis	`{{ "hello world" \| truncate: 8 }}` → `hello...`
`strip`	Remove whitespace	`{{ " hello " \| strip }}` → `hello`
`replace`	Replace text	`{{ "hello" \| replace: "e", "a" }}` → `hallo`
`split`	Split into array	`{{ "a,b,c" \| split: "," }}` → array

Number Filters

Filter	Description	Example
`plus`	Add numbers	`{{ 5 \| plus: 3 }}` → `8`
`minus`	Subtract	`{{ 5 \| minus: 3 }}` → `2`
`times`	Multiply	`{{ 5 \| times: 3 }}` → `15`
`divided_by`	Divide	`{{ 10 \| divided_by: 2 }}` → `5`
`round`	Round number	`{{ 4.6 \| round }}` → `5`

Array Filters

Filter	Description	Example
`size`	Array length	`{{ inputs.items \| size }}`
`first`	First element	`{{ inputs.items \| first }}`
`last`	Last element	`{{ inputs.items \| last }}`
`join`	Join with separator	`{{ inputs.items \| join: ", " }}`
`sort`	Sort array	`{{ inputs.items \| sort }}`
`reverse`	Reverse order	`{{ inputs.items \| reverse }}`
`uniq`	Remove duplicates	`{{ inputs.items \| uniq }}`

Control Flow

If / Else

{% if inputs.tone == "formal" %}
Please respond in a formal, professional manner.
{% elsif inputs.tone == "casual" %}
Keep the response casual and friendly.
{% else %}
Use a neutral, balanced tone.
{% endif %}

Unless

{% unless inputs.skip_examples %}
Here are some examples to guide you:
- Example 1
- Example 2
{% endunless %}

Case / When

{% case inputs.format %}
  {% when "json" %}
    Return your response as valid JSON.
  {% when "markdown" %}
    Format your response using Markdown.
  {% when "plain" %}
    Return plain text without formatting.
  {% else %}
    Use your best judgment for formatting.
{% endcase %}

Loops

For Loop

Process the following items:
{% for item in inputs.items %}
- {{ forloop.index }}. {{ item }}
{% endfor %}

Loop Variables

Variable	Description
`forloop.index`	Current iteration (1-based)
`forloop.index0`	Current iteration (0-based)
`forloop.first`	True if first iteration
`forloop.last`	True if last iteration
`forloop.length`	Total iterations

Loop Example with Conditions

{% for category in inputs.categories %}
{% if forloop.first %}Categories to analyze:{% endif %}
  - {{ category | capitalize }}
{% if forloop.last %}
Please evaluate the content against all listed categories.
{% endif %}
{% endfor %}

Working with Objects

Access nested properties with dot notation:

Customer: {{ inputs.customer.name }}
Address: {{ inputs.customer.address.city }}, {{ inputs.customer.address.country }}

Iterate Over Object Properties

{% for item in inputs.metadata %}
  {{ item[0] }}: {{ item[1] }}
{% endfor %}

Including Snippets

Reuse common template fragments with includes:

{% include 'json-output-instructions' %}
{% include 'tone-guidelines' %}

Snippets are defined in the Prompt Snippets section. See Working with Snippets for details.

Real-World Examples

Email Generator

Write a {{ inputs.tone | default: "professional" }} email for the following situation:

Subject: {{ inputs.subject }}
Recipient: {{ inputs.recipient_name }}
Context: {{ inputs.context }}

{% if inputs.key_points %}
Key points to include:
{% for point in inputs.key_points %}
- {{ point }}
{% endfor %}
{% endif %}

{% if inputs.max_length %}
Keep the email under {{ inputs.max_length }} words.
{% endif %}

Return the email with a clear subject line and body.

Content Classifier

Classify the following {{ inputs.content_type | default: "text" }} into one of these categories:
{% for category in inputs.categories %}
- {{ category }}
{% endfor %}

Content to classify:
{{ inputs.content | truncate: 5000 }}

{% include 'json-output-instructions' %}

Return:
{
  "category": "selected category",
  "confidence": 0.0 to 1.0,
  "reasoning": "brief explanation"
}

Multi-Language Support

{% case inputs.language %}
  {% when "es" %}
    Responde en español.
  {% when "fr" %}
    Répondez en français.
  {% when "de" %}
    Antworten Sie auf Deutsch.
  {% else %}
    Respond in English.
{% endcase %}

{{ inputs.instruction }}

Content: {{ inputs.content }}

Best Practices

Always use defaults

Optional fields should have sensible defaults to prevent empty values in prompts.

Truncate long inputs

Use truncate to prevent extremely long inputs from exceeding token limits.

Use includes for reusability

Common instructions (JSON formatting, tone guidelines) should be snippets.

Test edge cases

Test with empty arrays, missing optional fields, and unusual values.

Keep logic simple

Complex logic is hard to debug. Keep conditionals straightforward.

Debugging Templates

If your template isn’t working:

Check the rendered preview in the prompt editor
Verify input field names match exactly
Test with simple values first
Check for typos in filter names
Ensure conditionals have proper endif / endfor tags

Basic Syntax

Variable Output

Filters

Tags

Accessing Input Values

Default Values

Common Filters

String Filters

Number Filters

Array Filters

Control Flow

If / Else

Unless

Case / When

Loops

For Loop

Loop Variables

Loop Example with Conditions

Working with Objects

Iterate Over Object Properties

Including Snippets

Real-World Examples

Email Generator

Content Classifier

Multi-Language Support

Best Practices

Debugging Templates

Next Steps

Create a Prompt

Prompt Snippets

​Basic Syntax

​Variable Output

​Filters

​Tags

​Accessing Input Values

​Default Values

​Common Filters

​String Filters

​Number Filters

​Array Filters

​Control Flow

​If / Else

​Unless

​Case / When

​Loops

​For Loop

​Loop Variables

​Loop Example with Conditions

​Working with Objects

​Iterate Over Object Properties

​Including Snippets

​Real-World Examples

​Email Generator

​Content Classifier

​Multi-Language Support

​Best Practices

​Debugging Templates

​Next Steps

Create a Prompt

Prompt Snippets

Basic Syntax

Variable Output

Filters

Tags

Accessing Input Values

Default Values

Common Filters

String Filters

Number Filters

Array Filters

Control Flow

If / Else

Unless

Case / When

Loops

For Loop

Loop Variables

Loop Example with Conditions

Working with Objects

Iterate Over Object Properties

Including Snippets

Real-World Examples

Email Generator

Content Classifier

Multi-Language Support

Best Practices

Debugging Templates

Next Steps