wbcreateclaim

var api = new mw.Api();
api.get({
  action:'query',
  continue:'',
  meta:'tokens',
  format:'json'
}).done(function(token) {
  api.post({
    action: 'wbcreateclaim',
    entity: 'Q4115189',
    property: 'P901',
    snaktype: 'value',
    token: token.query.tokens.csrftoken,
    value: {'entity-type': "item", 'numeric-id':1}
  }).done(function(data) {
    console.log(data);
  });
});

/*
Error message

{
    "servedby": "mw1131",
    "warnings": {
        "main": {
            "*": "Parameter 'value' uses unsupported PHP array syntax"
        }
    },
    "error": {
        "code": "param-missing",
        "info": "A parameter that is required was missing (A value needs to be provided when creating a claim with PropertyValueSnak snak)",
        "messages": [
            {
                "name": "wikibase-api-param-missing",
                "parameters": [],
                "html": {
                    "*": "A parameter that is required was missing"
                }
            }
        ],
        "*": "See https://www.wikidata.org/w/api.php for API usage"
    }
}
*/