Many traveling arrangements can be made online at this time, such as lodging, transportation, and choosing tourist attractions. Studies on online tourism systems discuss a lot about booking service systems at hotel reservations, transportation reservations, or booking tour tickets. However, most of these studies were carried out only on individual processes and were not integrated. This study built a web service for travel package booking that allows travelers to book transportation, hotels, and travel tickets in one transaction. The use of API technology combines parameters from ordering a travel package, then carrying out a comprehensive calculation. In the end, travelers will get many options to combine their travel packages automatically. In this study, the validity of the API was tested. Testing the API built resulted in an average time of 2946 ms from 50 trials of API calls by ten different users accessing the system simultaneously. We suggest adding API connections with providers of travel location review information so that more details will be available in one particular place.