diff --git a/src/main/proto/wfa/measurement/api/v2alpha/measurement_spec.proto b/src/main/proto/wfa/measurement/api/v2alpha/measurement_spec.proto
index c175221c..82b57a00 100644
--- a/src/main/proto/wfa/measurement/api/v2alpha/measurement_spec.proto
+++ b/src/main/proto/wfa/measurement/api/v2alpha/measurement_spec.proto
@@ -144,4 +144,33 @@ message MeasurementSpec {
     (google.api.resource_reference).type = "halo.wfanet.org/ModelLine",
     (google.api.field_behavior) = IMMUTABLE
   ];
+
+  // Metadata provided by the Reporting System that describes how the
+  // Measurement is being used.
+  message ReportingMetadata {
+    // Resource name of the containing `Report`
+    string report = 1 [
+      (google.api.field_behavior) = REQUIRED,
+      (google.api.field_behavior) = IMMUTABLE,
+      (google.api.resource_reference) = {
+        type: "reporting.halo-cmm.org/Report"
+      }
+    ];
+    // Resource name of the containing `Metric`
+    string metric = 2 [
+      (google.api.field_behavior) = REQUIRED,
+      (google.api.field_behavior) = IMMUTABLE,
+      (google.api.resource_reference) = {
+        type: "reporting.halo-cmm.org/Metric"
+      }
+    ];
+  }
+  // Metadata provided by the Reporting System.
+  //
+  // When present the report_metadata can be used by EDPs to group Measurements
+  // into logical units to help optimize fulfilment processes.
+  ReportingMetadata reporting_metadata = 11 [
+    (google.api.field_behavior) = OPTIONAL,
+    (google.api.field_behavior) = IMMUTABLE
+  ];
 }