Is there an option type for only Voice Channels in discord_slash?

Although I don’t have any experience with discord.py-interactions in particular (the library of discord-slash, renamed from discord-py-slash-command), but I’ve done some research and testing on this library. Here’s my findings:

Is it possible to specify only voice channels through Discord API? Yes definitely. But not natively with discord-slash. You’ll need to apply the following workaround:

only_vc_option = create_option(
    name="choice",
    description="You can only choose a VC!",
    option_type=SlashCommandOptionType.CHANNEL,
    required=True
)
only_vc_option['channel_types'] = [2]


@slash.slash(name="test",
             description="This is just a test command.",
             options=[only_vc_option])
async def test(ctx, choice: discord.VoiceChannel):
    await ctx.send(content=f"You chose {choice}, which is a {type(choice)}!")

discord-slash doesn't have any support to specify the channel type explicitly, but it also doesn't sanitize the options dict that gets passed to Discord API. Therefore, it is possible to create the option as usual, then add the channel_types key and set it to a list of only 2 (voice channel type). And when you type-hint discord.VoiceChannel, discord.py does the proper channel conversion for you.

As a footnote, discord.py-interactions isn't well maintained nor documented, perhaps try out some other active libraries such as disnake which is discord.py combined with dislash. (I have no affiliations, just a recommendation)

No. The official Discord docs show that the only type you can use is CHANNEL (value 7), and it

Includes all channel types + categories

EDIT: I'm blind, use channel_types

channel_types? - array of channel types: if the option is a channel type, the channels shown will be restricted to these types

https://discord.com/developers/docs/resources/channel#channel-object-channel-types