diff --git a/id-match-1.2.yml b/id-match-1.2.yml
index 011e8c9..51cceec 100644
--- a/id-match-1.2.yml
+++ b/id-match-1.2.yml
@@ -146,6 +146,7 @@ paths:
                 candidates:
                   - confidence: '85'
                     referenceId: M219488003
+                    explanation: Family name exact match, given name initial match
                     attributes:
                       - sor: HRMS
                         identifiers:
@@ -422,6 +423,9 @@ components:
                 type: integer
               referenceId:
                 type: string
+              explanation:
+                type: string
+                description: optional; rationale for including this candidate              
               attributes:
                 type: array
                 items: