Related forum post: https://community.blackbaud.com/forums/viewtopic/494/59896
When creating a gift, and marking that gift as acknowledged, you can select an "Acknowledgement Letter" to relate to that gift.
However, there is no way currently to obtain a list of Acknowledgment Letter names through the API (without being a non-admin user that is)
This requests that a new endpoint, like https://api.sky.blackbaud.com/gift/v1/giftacknowledgements/ , be added that returns all Acknowledgement Letter names:
{
"count": 1,
"value": [
{
"name": "Duck letter"
},
]
}