Alexa: invalid option for entity_config name - noob question

just got my alexa working, now i wanna name an entity with the entity_config:

    entity_config:
      pck:
        name: "PC-Kobito"
        description: "Kobitos'PC an und ausmachen"
        display_categories: SWITCH

it say pck is an invalid name for alexa, where can i check whats valid ?
pck is my entity to switch my pc on and off

getting: Invalid config for [alexa]: [pck] is an invalid option for [alexa]. Check: alexa->alexa->smart_home->entity_config->pck. (See /config/configuration.yaml, line 19).

using Amazon Alexa Smart Home Skill - Home Assistant

What are valid options to name an entity ?

read alot about the naming convention of entities and got it to work