> ## Documentation Index
> Fetch the complete documentation index at: https://docs.workflowmachine.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Expression syntax

> Learn the basics of using expressions and templated values inside workflow fields.

## Why expressions matter

Expressions help you build dynamic workflows.

They let steps use values from earlier parts of the workflow instead of relying only on static text or fixed configuration.

## Template style

Workflow Machine uses `{{ ... }}` style expressions.

This is useful when:

* a later step needs data from the trigger
* one step depends on the output of another
* field values should be built dynamically

## Common uses

Expressions are especially useful for:

* building message content
* selecting output fields
* combining values into a readable string
* passing workflow data from one step into another

## Keep expressions simple first

When you start using expressions, prefer simple references over complicated logic.

That makes workflows:

* easier to read
* easier to test
* easier to troubleshoot

If an expression becomes difficult to understand, it may be a sign that some of the logic belongs in a separate step instead.

## A few important rules

The expression system in Workflow Machine includes a few important behaviors:

* expressions use `{{ ... }}` syntax
* arrays use 1-based indexing
* negative indices count from the end

These details matter when you start working with lists and step outputs.

## Best practice

Whenever an expression is important to the workflow result, test the step output that depends on it before publishing. Dynamic values are powerful, but they are easiest to trust when you have seen them work with real data.