Using simple template in Blueprint generates error 'required key not provided'

I noticed that using minimal jinja template to provide a value for a data param in action in Blueprint throws an error. The only difference in this test is {{ 50 }} instead of 50.

Minimal example

Code below works without problems

action:
- service: light.turn_on
  target: !input light_target
  data:
    brightness: 50 

Code below generates error: Invalid blueprint: required key not provided @ data['blueprint']. Got None

action:
- service: light.turn_on
  target: !input light_target
  data:
    brightness: {{ 50 }}

What I am doing wrong? The same behavior is for {{ (50) }}.

It’s a super simplified example, since I struggled with similar error while using variables and calculations. This minimal example crashes bluepring loader.

This one was tricking. Despite the fact that brightness is of type integer, you have to use double quotation when using template values, i.e.

action:
- service: light.turn_on
  target: !input light_target
  data:
    brightness: "{{ 50 }}"

Same goes to calculated values, even if the yaml type is integer.

But the error from Blueprint loader was very confusing. Moreover, in the system loads the error message suggests the blueprint file could not be found!

Invalid config for [automation]: Failed to load blueprint: Unable to find my_blueprints/motion_light_with_time_brightness.yaml (See /config/configuration.yaml, line 8).