How to set default value to metafields : ID won't be given unless you fill the field on UI?

Retired Boards Appdev Metafields
7

@Charlie-SLA
PUT: products/{product_id}/metafiels/22414790557925.json {“metafiled”:{“value”:true}}

To all products came through.
Then if I call

GET: products/{product_id}/metafiels/22414790557925.json
It returns {“value”:true} with the same type and field name although this won’t be in a list of metafields. = GET: products/{a product’s id}/metafiels.json

Strange still but it surved my purpose anyway.