Uniqueness validation is built into the collections API. If you attempt to add a model with a duplicate ID you'll get a 400 error. In addition you can specify v

Uniqueness validation is built into the collections API. If you attempt to add a model with a duplicate ID you'll get a 400 error. In addition you can specify validation rules in the config.yml file. Some additional info here: http://backlift.github.com/docs/validation.html#validation-rule-reference http://backlift.github.com/docs/validation.html#validation-r.... As for query parameters on the collections API, we totally agree it's a must and we're working on it.