I can't get access token from Amadeus Flight API authentication process using requests and oauth_lib. https://developers.amadeus.com/self...eys/authorization/#requesting-an-access-token Using Requests import requests API_KEY = "twAtndd5V..." API_SECRET = "xtj..." AUTH_ENDPOINT = "https://test.api.amadeus.com/v1/security/oauth2/token/" head = {"Content-Type" : "application/x-www-form-urlencoded"} response = requests.post( url=AUTH_ENDPOINT, json={"grant_type" : "client_credentials", "client id" : API_KEY, "client_secret" : API_SECRET}, headers=head ) print(response.text) { "error":"invalid_request", "error_description": "No access_token parameter needed for this method", "code": 38187, "title": "Invalid parameters" } Try with oauth2 https://requests-oauthlib.readthedocs.io/en/latest/oauth2_workflow.html#backend-application-flow from requests_oauthlib import OAuth2Session from oauthlib.oauth2 import BackendApplicationClient client = BackendApplicationClient(client_id=API_KEY) oauth = OAuth2Session(client=client) token = oauth.fetch_token(token_url=AUTH_ENDPOINT, client_id=API_KEY, client_secret=API_SECRET) token = oauth.fetch_token(token_url=AUTH_ENDPOINT, client_id=API_KEY, client_secret=API_SECRET) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\asdf\AppData\Local\Programs\Python\Python312\Lib\site-packages\requests_oauthlib\oauth2_session.py", line 406, in fetch_token self._client.parse_request_body_response(r.text, scope=self.scope) File "C:\Users\asdf\AppData\Local\Programs\Python\Python312\Lib\site-packages\oauthlib\oauth2\rfc6749\clients\base.py", line 427, in parse_request_body_response self.token = parse_token_response(body, scope=scope) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\asdf\AppData\Local\Programs\Python\Python312\Lib\site-packages\oauthlib\oauth2\rfc6749\parameters.py", line 441, in parse_token_response validate_token_parameters(params) File "C:\Users\asdf\AppData\Local\Programs\Python\Python312\Lib\site-packages\oauthlib\oauth2\rfc6749\parameters.py", line 448, in validate_token_parameters raise_from_error(params.get('error'), params) File "C:\Users\asdf\AppData\Local\Programs\Python\Python312\Lib\site-packages\oauthlib\oauth2\rfc6749\errors.py", line 399, in raise_from_error raise cls(**kwargs) oauthlib.oauth2.rfc6749.errors.InvalidClientIdError: (invalid_request) No access_token parameter needed for this method Continue reading...