NSL filter and function reference

NSL (Newo Script Language) is built on Jinja2. In addition to standard Jinja2 filters and tests, the platform provides NSL-specific actions and a small set of custom filters. This page lists all available filters and custom functions.

Standard Jinja2 filters

All standard Jinja2 filters are available in NSL. Commonly used filters include:

Filter	Example	Description
`upper`	`{{ value\|upper }}`	Converts a string to uppercase.
`lower`	`{{ value\|lower }}`	Converts a string to lowercase.
`trim`	`{{ value\|trim }}`	Strips leading and trailing whitespace.
`replace`	`{{ value\|replace("old", "new") }}`	Replaces all occurrences of a substring.
`default`	`{{ value\|default("fallback") }}`	Returns the default value if `value` is undefined or falsy.
`int`	`{{ value\|int }}`	Converts a value to integer.
`float`	`{{ value\|float }}`	Converts a value to float.
`string`	`{{ value\|string }}`	Converts a value to string.
`length`	`{{ value\|length }}`	Returns the length of a string, list, or dict.
`join`	`{{ list\|join(", ") }}`	Joins a list into a string using the separator.
`split`	`{{ value\|split(",") }}`	Splits a string into a list on the delimiter.
`first`	`{{ list\|first }}`	Returns the first item in a list.
`last`	`{{ list\|last }}`	Returns the last item in a list.
`sort`	`{{ list\|sort }}`	Sorts a list.
`unique`	`{{ list\|unique }}`	Returns unique items from a list.
`tojson`	`{{ value\|tojson }}`	Serializes a value to JSON string.
`fromjson`	`{{ value\|fromjson }}`	Parses a JSON string into a Python object.
`truncate`	`{{ value\|truncate(100) }}`	Truncates a string to the given number of characters.
`round`	`{{ value\|round(2) }}`	Rounds a number to the given number of decimal places.
`abs`	`{{ value\|abs }}`	Returns the absolute value of a number.
`bool`	`{{ value\|bool }}`	Converts a value to boolean.

NSL-specific behaviors

Block scoping

NSL does not use standard Jinja2 block scoping. Variables set with {% set %} inside {% if %} or {% for %} blocks are accessible outside those blocks. This differs from standard Jinja2 behavior.

{% if condition %}
  {% set result = "yes" %}
{% else %}
  {% set result = "no" %}
{% endif %}

{# result is accessible here in NSL — it would be undefined in standard Jinja2 #}
{{ result }}

Output suppression

Use {%- -%} to suppress whitespace around block tags:

{%- set x = GetCustomerAttribute(field="project_attributes_business_name") -%}

Using {% set %} without - trimming will produce empty lines in the output. For assignments that should produce no output, use {%- -%}.

Comments

Single-line: {# This is a comment #}

Multi-line:

{##
  This is a
  multi-line comment
##}

Role tags

NSL uses role tags to structure the content passed to the LLM in Gen() and GenStream() calls:

Tag	Description
`<system>...</system>`	System prompt content. Sets context, instructions, and persona.
`<user>...</user>`	User turn content. Represents the human's input.
`<assistant>...</assistant>`	Assistant turn content. Represents prior agent responses.

Role tags are only meaningful inside Gen() / GenStream() calls. Outside of generation calls, they are treated as literal strings.

Custom NSL actions used as expressions

Actions that return values and are commonly used as expressions within {% set %} or {{ }}:

Action	Returns	Common use
`GetCustomerAttribute(field)`	string / any	Read a customer attribute value
`GetPersonaAttribute(field)`	string / any	Read a persona attribute value
`GetProjectAttribute(field)`	string / any	Read a project attribute value
`GetState(name)`	any	Read a state field value
`GetUser(field)`	string / any	Read a user field (e.g., `id`, `name`, `email`)
`GetSessionInfo(field)`	string / any	Read session metadata
`GetDatetime(format)`	string	Current date and time in the specified format
`IsEmpty(value)`	bool	Check if a value is null, empty string, or empty list
`IsSimilar(a, b, threshold)`	bool	Check if two strings are semantically similar
`Concat(a, b)`	string	Concatenate two strings
`Stringify(value)`	string	Convert any value to a string representation
`GetRandomChoice(list)`	any	Return a random item from a list
`GetValueJSON(json, path)`	any	Extract a value from a JSON object by path