diff --git a/docs/docs/docs/01-core/data-transfer/01-engine.md b/docs/docs/docs/01-core/data-transfer/01-engine.md
index 3a323a8908..c7d4720036 100644
--- a/docs/docs/docs/01-core/data-transfer/01-engine.md
+++ b/docs/docs/docs/01-core/data-transfer/01-engine.md
@@ -197,9 +197,27 @@ The following events are available:
 
 ### Diagnostics events
 
-`engine.diagnostics.onDiagnostic(formatDiagnostic('export'));`
+The engine includes a diagnostics reporter which can be used to listen for diagnostics information (debug messages, errors, etc).
 
-**TODO**
+Here is an example for creating a diagnostics listener:
+
+```
+// your listener
+engine.diagnostics.onDiagnostic(async (data: GenericDiagnostic) => {
+  // handle the diagnostics, for example with custom logging
+});
+
+// engine/diagnostics.ts - format of the data sent to the listener
+export type GenericDiagnostic<K extends DiagnosticKind, T = unknown> = {
+  kind: K;
+  details: {
+    message: string;
+    createdAt: Date;
+  } & T;
+};
+
+export type DiagnosticKind = 'error' | 'warning' | 'info';
+```
 
 ### Transforms
 
diff --git a/packages/core/data-transfer/src/engine/diagnostic.ts b/packages/core/data-transfer/src/engine/diagnostic.ts
index 7f303d9ab2..7aa7dfdecb 100644
--- a/packages/core/data-transfer/src/engine/diagnostic.ts
+++ b/packages/core/data-transfer/src/engine/diagnostic.ts
@@ -15,7 +15,7 @@ export type GenericDiagnostic<K extends DiagnosticKind, T = unknown> = {
 export type DiagnosticKind = 'error' | 'warning' | 'info';
 
 export type DiagnosticListener<T extends DiagnosticKind = DiagnosticKind> = (
-  diagnostic: { kind: T } & Diagnostic extends infer U ? U : 'foo'
+  diagnostic: { kind: T } & Diagnostic extends infer U ? U : never
 ) => void | Promise<void>;
 
 export type DiagnosticEvent = 'diagnostic' | `diagnostic.${DiagnosticKind}`;