Variables

Learn how to access variables, follow valid variable naming rules, and safely use escaped names when working with FEEL expressions.

Access variables

Access the value of a variable by its variable name.

FEEL doesn't use a separate assignment operator to create or update process variables. Instead, FEEL evaluates variables that are already available in the current context, or you can define local values with context entries.

a + b

If the value of the variable is a context, a context entry can be accessed by its key.

a.b

For example, in an AI agentAI agentAn addressable execution of an LLM-driven loop with shared memory context across iterations. An agent runs an agent loop where the model decides what to do next, which tools to invoke, and when to stop. tool definition, the toolCall variable is a context holding the parameters an LLM supplies at runtime. See fromAi() for how tool parameters are declared.

If no variable exists with the given name, the expression returns null.

tip

Use a null-check if the variable can be null or is optional.

a != null and a.b > 10

Variable names

The name of a variable can be any alphanumeric string including the _ symbol. For a combination of words, it's recommended to use the camelCase or the snake_case format. The kebab-case format is not allowed because it contains the operator -.

When accessing a variable in an expression, keep in mind the variable name is case-sensitive.

Restrictions of a variable name:

• It may not start with a number (e.g. 1stChoice is not allowed; you can use firstChoice instead).
• It may not contain whitespaces (e.g. order number is not allowed; you can use orderNumber instead).
• It may not contain an operator (e.g. +, -, *, /, =, >, <, ?, .).
• It may not be a literal (e.g. null, true, false) or a keyword (e.g. function, if , then, else, for, return, between, instance, of, not, in, and, or, some, every, satisfies).

Escape variable names

Camunda Extension

If a variable name or a context key contains any special character (e.g. whitespace, dash, etc.) then the name can be wrapped into single backquotes/backticks (e.g. `foo bar`).

`first name`

`tracking-id`

order.`total price`

tip

Use the get value() function to retrieve the context value of an arbitrary key.

get value(order, "total price")