CONVERT: Improve command consistency.

src/cli/msg.yml

@@ -115,3 +115,20 @@ errors:
       - "\nMake sure the options file contains valid JSON."
   optionsFileNotFound:
     msg: "The specified options file is missing or inaccessible."
+  unknownSchema:
+    msg:
+      - "Unknown resume schema. Did you specify a valid FRESH or JRS resume?"
+      - |
+          At a minimum, a FRESH resume must include a "name" field and a "meta"
+          property.
+
+          "name": "John Doe",
+          "meta": {
+            "format": "FRESH@0.1.0"
+          }
+
+          JRS-format resumes must include a "basics" section with a "name":
+
+          "basics": {
+            "name": "John Doe"
+          }