Function Provider SPI: custom function


I’m testing the Function Provider SPI from the docs.

I am extending the Zeebe DMN Worker to include the custom function decr. I have a created a file named org.camunda.feel.context.CustomFunctionProvider with the following content:


CustomJavaFunctionProvider is the custom class declared in the package io.zeebe.dmn.

I get this error after execution:

failed to evaluate expression ‘{season: “Winter”,guestCount: decr(4),guestsWithChildren: true}’: no function found with name ‘decr’ and 1 parameters

Could you please help? What am I missing here?

Thank you,

Since this is a Camunda Cloud (Zeebee) question, it might get more attention and a better answer over at the Cloud Forums:


Hi @y-io,

thank you for raising this up!

Currently, this feature is not supported by the worker. The worker uses the Camunda DMN engine which has a slightly different way to register custom functions. But the worker doesn’t provide an option to register the functions like described.

As a workaround, you could try to set the expression language to feel-scala. This forces the DMN engine to call the FEEL engine as a script language.

Please create a new feature request in the worker repo.

Best regards,