Template functions provide simple text transformations for common operations like converting to lowercase, URL encoding, and date formatting. They complement JavaScript expressions by handling specific formatting tasks that don’t require complex logic.

For information about variable scopes, see the Variables Reference. For JavaScript expressions and data manipulation, see the Expressions Reference.

Template functions are only available in SWAIG (SignalWire AI Gateway) contexts, specifically within:

• AI function data_map processing (expressions, webhooks, output)
• Webhook responses to SWAIG functions
• AI prompt variable expansion

They are not available in regular SWML methods or general variable contexts. For regular SWML variable manipulation, use JavaScript expressions with the ${expression} syntax instead.

Reference

lc

string

Converts a string to lowercase. Commonly used to normalize user input for case-insensitive comparisons or ensure consistent casing when accessing object properties dynamically.

Syntax:${lc:<value>}

Example:

YAMLJSON

SWAIG:
    functions:
      - function: lookup
        description: Look up department contact
        parameters:
          type: object
          properties:
            department:
              type: string
              description: Department name from user
        data_map:
          expressions:
            - string: '${meta_data.contacts.${lc:args.department}}'
              pattern: '\w+'
              output:
                response: "Found contact for ${args.department}"
        meta_data:
          contacts:
            sales: '+12025551234'
            support: '+12025555678'

enc:url

string

Encodes a string for safe use in URLs by converting special characters to percent-encoded equivalents. Always use this when including variables in URL query parameters or paths to prevent special characters from breaking URLs or causing unexpected behavior.

Syntax:${enc:url:<value>}

Example:

YAMLJSON

SWAIG:
    functions:
      - function: search
        description: Search external knowledge base
        parameters:
          type: object
          properties:
            query:
              type: string
              description: User's search query
        data_map:
          webhooks:
            - url: 'https://api.example.com/search?q=${enc:url:args.query}'
              method: GET
              output:
                response: "Found ${results.total} results for ${args.query}"

strftime_tz

string

Formats the current date and time using standard strftime format codes with timezone support. This generates timestamps at the moment the template is evaluated, not when the SWML script was created.

Syntax:@{strftime_tz <timezone> <format>}

Common format codes:

Code	Description	Example
%Y-%m-%d	ISO date	2025-01-15
%H:%M:%S	24-hour time	14:30:45
%I:%M %p	12-hour time	02:30 PM
%A, %B %d, %Y	Full readable date	Monday, January 15, 2025

Example:

YAMLJSON

SWAIG:
    functions:
      - function: log_call
        description: Log call details with timestamp
        data_map:
          webhooks:
            - url: 'https://api.example.com/logs'
              method: POST
              params:
                timestamp: '@{strftime_tz America/Chicago %Y-%m-%d %H:%M:%S}'
                call_id: '${call.call_id}'
                from: '${call.from}'
              output:
                response: "Call logged successfully"

fmt_ph

string

Formats a phone number using specified international format standards. Supports multiple format types for different use cases, with optional separators for improved text-to-speech pronunciation.

Syntax:@{fmt_ph <format> <phone_number>} or @{fmt_ph <format>:sep:<separator> <phone_number>}

Available formats:

• national - National format (default)
• international - International format with country code
• RFC3966 - RFC 3966 format (tel: URI)
• e164 - E.164 format (+1234567890)

Example:

YAMLJSON

SWAIG:
    functions:
      - function: format_number
        description: Format phone number for speech
        data_map:
          output:
            response: |
              International format: @{fmt_ph international ${call.from}}
              Spaced format: @{fmt_ph national:sep:- ${call.from}}

expr

string

Evaluates simple arithmetic expressions with literal numbers. Supports addition, subtraction, multiplication, division, and parentheses for grouping. Only works with literal numbers and cannot reference variables.

Syntax:@{expr <expression>}

Example:

YAMLJSON

SWAIG:
    functions:
      - function: calculate_discount
        description: Calculate discount amount
        data_map:
          output:
            response: "The discount is @{expr (100 - 25) / 5} dollars"

echo

string

Returns the argument unchanged. Primarily useful for debugging template evaluation or forcing explicit variable expansion in complex nested scenarios.

Syntax:@{echo <text>}

Example:

YAMLJSON

SWAIG:
    functions:
      - function: debug_value
        description: Debug template evaluation
        parameters:
          type: object
          properties:
            input:
              type: string
              description: Value to debug
        data_map:
          output:
            response: "Debug value: @{echo ${args.input}}"

separate

string

Inserts spaces between each character in a string to improve text-to-speech pronunciation. Particularly useful for spelling out confirmation codes, license plates, serial numbers, or any text that should be read character-by-character.

Syntax:@{separate <text>}

Example:

YAMLJSON

SWAIG:
    functions:
      - function: spell_code
        description: Spell out confirmation code
        parameters:
          type: object
          properties:
            code:
              type: string
              description: Confirmation code to spell
        data_map:
          output:
            response: "Your code is @{separate ${args.code}}"

In this example, if code is “ABC123”, the AI will pronounce “A B C 1 2 3” instead of trying to say “ABC123” as a word.

sleep

string

Pauses execution for the specified number of seconds. Can be used for rate limiting, timing coordination, or testing purposes.

Syntax:@{sleep <seconds>}

Use sparingly in production environments. Excessive delays can cause timeouts, impact call quality, and degrade user experience. Best suited for development, testing, or specific rate-limiting scenarios.

Example:

YAMLJSON

SWAIG:
    functions:
      - function: delayed_task
        description: Execute with delay for rate limiting
        data_map:
          output:
            response: "Executed after @{sleep 2} second delay"

Function chaining

Prefix functions (using ${...} syntax) can be chained together to apply multiple transformations in sequence. The transformations are applied from left to right.

Syntax:${func1:func2:func3:<value>}

Example:

YAMLJSON

SWAIG:
  functions:
    - function: search
      description: Search external knowledge base
      parameters:
        type: object
        properties:
          query:
            type: string
            description: User's search query
      data_map:
        webhooks:
          # First converts to lowercase, then URL encodes
          - url: 'https://api.example.com/search?q=${lc:enc:url:args.query}'
            method: GET
            output:
              response: "Found results for ${args.query}"

Full example

YAMLJSON

version: 1.0.0
sections:
  main:
    - answer: {}
    - ai:
        prompt:
          text: |
            You help users access department resources.
            When they specify a department, use the lookup function.
        SWAIG:
          functions:
            - function: lookup
              description: Look up department contact
              parameters:
                type: object
                properties:
                  department:
                    type: string
                    description: Department name from user
              data_map:
                expressions:
                  - string: '${meta_data.contacts.${lc:args.department}}'
                    pattern: '\w+'
                    output:
                      response: "Found contact for ${args.department}"
              meta_data:
                contacts:
                  sales: '+12025551234'
                  support: '+12025555678'