G-Sheet script to post a message on Guilded using its API - api

Question

I am trying to create a script to post a text message in a chat on Guilded, but so far I get a "POST is not allowed"
Message should be "inPrivate" so a mention of the targeted member is required.
Google sheet test file
my script:
function message () {
var url = "https://www.guilded.gg/api/v1/channels/";
var channelid = "d2ba*****";
var key = "Bearer gapi_*****"; //Q-P API temp-bot
const message = {
content : "It's alive!",
embeds :[{
author:"API",
mentions:"Raven_test",
}],
isPrivate : true,
}
const params = {
method: "POST",
headers: { Authorization: key },
contentType: "application/json",
payload: JSON.stringify(message),
muteHttpExceptions: true,
};
Logger.log(JSON.stringify(params));
const response = UrlFetchApp.fetch(url + channelid + "/messages/", params);
var data = JSON.parse(response);
Logger.log(data);
}
Guilded's API
I don't understand what I'm doing wrong (but I'm a newbie, so it makes sens)

Answer 1

POST is still not working, with the same answer, however, if I use the PUT method, I can update a message if written by the same bot (I just need to add the messageid in the url after /messages/
function postmessage () {
var url = "https://www.guilded.gg/api/v1/channels/";
var channelid = "d2bac803-****-****-****-a609ab9c58c4";
var key = "Bearer gapi_******"; //Q-P API temp-bot
var server = "wlVKV***"
var messageid = "ae6f1693-****-****-****-c9984d4142de";
var author = "****";
const message = {
"type": "default",
"serverId":server,
"channelId":channelid,
"content" : "test #Aaron Raven ",
"mentions":{
"users" : [{"id":author}]
},
"isPrivate":false,
"isSilent":false
};
const params = {
method: "put",
headers: { Authorization: key },
contentType: "application/json",
payload: JSON.stringify(message),
muteHttpExceptions: true,
};
Logger.log(JSON.stringify(params));
// const response = UrlFetchApp.fetch(url + channelid + "/messages/" + messageid, params);
const response = UrlFetchApp.fetch(url + channelid + "/messages/" params);
var data = JSON.parse(response);
Logger.log(response);
Logger.log(data);
Logger.log(params);
}
Another issue (aside POST method) is that "mentions" doesn't work; it appears as basic text, and not as a user tag/link
Kind regards,