Whats the message in the body?
The HTTP Code is half the information needed to stolve this. The body should have a JSON body that contains a message which describes the issue.
You declared JSON as the Content-Type but your bdoy is not JSON. It’s an Object.
You may need to JSON.stringify
So
'body': {
'tag_ids': tags_array
}
becomes
'body': JSON.stringify({
'tag_ids': tags_array
})
This is irrelevant since the API uses YOUR token, not the bot’s token.