Endpoint: www.youtube.com/youtubei/v1/search
Endpoint (YTM): music.youtube.com/youtubei/v1/search
Method: POST

Search:
{
    context: ...,

    query: "hello"
    params: <optional>
}

Search params:
Videos "EgIQAQ%3D%3D"
Channels "EgIQAg%3D%3"
Playlists "EgIQAw%3D%3D"

-- from YTM web app ---
Music tracks "EgWKAQIIAWoKEAMQBBAFEAkQCg%3D%3D"
Music videos "EgWKAQIQAWoKEAMQBBAFEAkQCg%3D%3D"
Music artists "EgWKAQIgAWoKEAMQBBAFEAkQCg%3D%3D"
Music albums "EgWKAQIYAWoKEAMQBBAFEAkQCg%3D%3D"
Music community playlists "EgeKAQQoAEABagoQAxAEEAUQCRAK"
Music official playlists "EgeKAQQoADgBagwQDhAKEAMQBBAJEAU%3D"

-- from NewPipe ---
Music tracks "Eg-KAQwIARAAGAAgACgAMABqChAEEAUQAxAKEAk%3D"
Music videos "Eg-KAQwIABABGAAgACgAMABqChAEEAUQAxAKEAk%3D"
Music artists "Eg-KAQwIABAAGAAgASgAMABqChAEEAUQAxAKEAk%3D"
Music albums "Eg-KAQwIABAAGAEgACgAMABqChAEEAUQAxAKEAk%3D"
Music playlists "Eg-KAQwIABAAGAAgACgBMABqChAEEAUQAxAKEAk%3D"

More search items:
{
    context: ...,

    continuation: "ErAFEgR0ZXN0GoQDU0JT..."
}

More search items (YTM)
Query params:
ctoken=EqMDEgpkZXV0c2NocG9wGpQDRWdXS0FRS... (=continuation, not necessary)
continuation=EqMDEgpkZXV0c2NocG9wGpQDRWdXS0FRS...
type=next