Impossible to get messages details in a list request with Gmail API - ruby-on-rails

Question

I am using a ruby on rails app which connects to the Gmail API. When I make a listrequest to get all the messages of one mailbox, I only get back an idand a threadId property for each message.
I tried to follow Gmail API Doc using the fields parameters to get other properties (title, date...). It doesn't work, whether I use the google-api-client gem in my app, or by doing a direct GET request.
Adding any other parameters to the request ends with a failure. Here is the url that works :
https://www.googleapis.com/gmail/v1/users/me/messages?fields=messages(id,threadId)
Am I forced to make one call per message or using batch requests to get relevant datas ? It seems a little heavy...

Answer 1

You first need to list messages like you've done, and then get each message in a separate request.
Request 1
GET https://www.googleapis.com/gmail/v1/users/me/messages?maxResults=1&access_token={ACCESS_TOKEN}
Response 1
{
"messages": [
{
"id": "15fd9f0fe242f975",
"threadId": "15fd9f0fe242f975"
}
],
"nextPageToken": "11889180580605610074",
"resultSizeEstimate": 2
}
Request 2
GET https://www.googleapis.com/gmail/v1/users/me/messages/15fd9f0fe242f975?access_token={ACCESS_TOKEN}
Response 2
{
"id": "15fd9f0fe242f975",
"threadId": "15fd9f0fe242f975",
"labelIds": [
"IMPORTANT",
"CATEGORY_UPDATES",
"INBOX"
],
"snippet": "Tasks tracked last week...",
"historyId": "966691",
...
}
It's also possible to get the total amount of request down from 1 + n of messages to 2 by using batch requests.