REI's Mountain Project (via Adventure Projects) is a crowd-sourced guide to climbing areas and routes built by climbers, providing a definitive climbing resource. Contributors add areas and routes, detailed descriptions, photos, ratings, and comments to bring you an extensive guide to climbing around the world, with more added on a daily basis.
The Mountain Project API provides simple access to certain limited data. All of the data returned by the API is already available on publicly available pages on the Mountain Project site. The API can return returns general user information, the user's most recent ticks (keeping track of what you've climbed), auser's to-dos, details for up to 200 routes, and routes for a given query. All requests require a private key that identifies you. Data is returned in JSON.
Usage of the API is at Mountain Project's sole discretion and may be discontinued at any time. Every request is tracked to be sure your code caches data and does not make excessive requests or your account will be deactivated.