MWS needs the POST data passed as form params instead of as a query string for some operations. Otherwise, it pukes a Failed processing arguments of org.jboss.resteasy.spi.metadata
style 400 Bad Request
error for some operations such as this one (GetMyFeesEstimate
is another that suffers from this).
For instance, if you did the following POST request in Guzzle 6 then you'd likely get the error:
$response = $client->request('POST', 'https://mws.amazonservices.com/Products/2011-10-01/?AWSAccessKeyId=YOURAWSACCESSKEY&Action=GetLowestPricedOffersForASIN&SellerId=YOURSELLERID&MWSAuthToken=amzn.mws.fghsffg-4t44e-hfgh-dfgd-zgsdbfe5erg&SignatureVersion=2&Timestamp=2017-07-09T15%3A45%3A18%2B00%3A00&Version=2011-10-01&Signature=bCasdxXmYDCasdaXBhsdgse4pQ6hEbevML%2FJvzdgdsfdy2o%3D&SignatureMethod=HmacSHA256&MarketplaceId=ATVPDKIKX0DER&ASIN=B007EZK19E');
To fix this you'd submit it as form data as in this Guzzle 6 example:
$response = $client->request('POST', 'https://mws.amazonservices.com/Products/2011-10-01', [
'form_params' => [
'AWSAccessKeyId' => 'YOURAWSACCESSKEY',
'Action' => 'GetLowestPricedOffersForASIN',
'SellerId' => 'YOURSELLERID',
'MWSAuthToken' => 'amzn.mws.fghsffg-4t44e-hfgh-dfgd-zgsdbfe5erg',
'SignatureVersion' => 2,
'Timestamp' => '2017-07-09T15%3A45%3A18%2B00%3A00',
'Version' => '2011-10-01',
'Signature' => 'bCasdxXmYDCasdaXBhsdgse4pQ6hEbevML%2FJvzdgdsfdy2o%3D',
'SignatureMethod' => 'HmacSHA256',
'MarketplaceId' => 'ATVPDKIKX0DER',
'ASIN' => 'B007EZK19E',
]
]);