Asset loader parameters in asset json file

[meigo]

Can't figure out how to add parameters to asset json file, for example:

"base":[ {"type":"com.badlogic.gdx.graphics.Texture", "path":"ui/default.png", "parameters": {"magFilter ": "Linear"}}, ... ] }

gives 'com.badlogic.gdx.utils.SerializationException: Field not found: magFilter (com.badlogic.gdx.assets.AssetLoaderParameters)'.

Guess the question is how to specify parameter type, TextureParameter in this case?