{{placeholders}} into your agent’s text and fill them with values while you test. You author them in the agent editor, and they ride the same draft → publish pipeline as the rest of the configuration.
Add a variable
Type{{ in the System prompt or First message field and give the variable a name, for example {{customer_name}}. Any custom token you use is picked up automatically — there’s nothing to declare separately.
Tokens that begin with system__ (such as {{system__time_utc}}) are reserved runtime values provided automatically, so they’re never listed as custom variables and don’t need a placeholder.
Set placeholder values
Open the{} Vars panel in the agent header. Every custom variable detected in your prompt and first message is listed with a type and a value:
Placeholder values are used when testing your agent in development — in the preview, each
{{variable}} in the system prompt and first message is replaced with its placeholder value so you can see a realistic conversation before publishing.