diff --git a/readme.md b/readme.md
index 5eff1f7..2598051 100644
--- a/readme.md
+++ b/readme.md
@@ -5,6 +5,20 @@ The FCVS API can be used by state medical boards (SMBs) to retrieve information
 
 To learn more about FSMB APIs, refer to the [Getting Started](https://github.com/fsmb/api-docs) guide. To learn more about this API and to begin using it in your code, please contact [FSMB](mailto:fcvs@fsmb.org).
 
+This API currently uses a custom error response instead of the standard [FSMB error response](https://github.com/fsmb/api-docs/docs/errors.md). The format of an error response is given here.
+
+```json
+{
+   "code": "Error code",
+   "message": "Descriptive message",
+   "target": "Optional target of the error",
+   "logId": "The ID of the log entry associated with the error, if any",
+   "innerError": { },
+   "data": { }
+}
+```
+
+If the error was caused by a lower level error, then `innerError` contains the error detail of the child error. Some errors may return additional data in the `data` property. The `code` field identifies the underlying error that occurred while the `message` field provides a developer friendly message.
 
 - URL
   - Demo: https://services-fcvs-demo.fsmb.org