Access to params in permissions

[Natchii59]

How I can access my Mutation/Query params to define my permissions.
For example, I can only put my id in the userId attribute which is passed as a parameter.

export const channelsPermissions: Permissions<null, Subjects, ChannelActions> =
  {
    everyone({ can, user }) {
      // const params = ???

      can(ChannelActions.join, Channel, {
        type: ChannelType.PUBLIC
      })
    }
  }