diff --git a/spec.yaml b/spec.yaml
index 3015bdb..8fe595d 100644
--- a/spec.yaml
+++ b/spec.yaml
@@ -325,6 +325,9 @@ paths:
                         items:
                           $ref: "#/components/schemas/LocalEvaluation"
                         description: Optional array of local evaluations
+                      error:
+                        type: string
+                        nullable: true
                     required:
                       - stepRuns
               required:
@@ -431,6 +434,9 @@ paths:
                         type: array
                         items:
                           $ref: "#/components/schemas/StepRun"
+                      error:
+                        type: string
+                        nullable: true
                     required:
                       - stepRuns
       responses:
@@ -578,6 +584,9 @@ paths:
                         items:
                           $ref: "#/components/schemas/LocalEvaluation"
                         description: Optional array of local evaluations
+                      error:
+                        type: string
+                        nullable: true
                     required:
                       - caseId
                       - inputs
@@ -649,6 +658,9 @@ paths:
                         type: object
                         additionalProperties: true
                         description: The returned outputs for the test case
+                      error:
+                        type: string
+                        nullable: true
                     required:
                       - caseId
                       - inputs
@@ -1860,6 +1872,10 @@ components:
               type: array
               items:
                 $ref: "#/components/schemas/TestEvaluation"
+            error:
+              type: string
+              nullable: true
+              description: Error message if the test run failed
 
     FullRun:
       type: object
@@ -1917,6 +1933,9 @@ components:
           additionalProperties:
             $ref: "#/components/schemas/MetadataValueObject"
           nullable: true
+        error:
+          type: string
+          nullable: true
 
     TestRun:
       type: object
@@ -2038,6 +2057,9 @@ components:
           type: array
           items:
             $ref: "#/components/schemas/StepRun"
+        error:
+          type: string
+          nullable: true
       required:
         - stepRuns
         - id
@@ -2085,6 +2107,9 @@ components:
         endTime:
           type: string
           format: date-time
+        error:
+          type: string
+          nullable: true
       required:
         - providerName
         - invocation
@@ -2126,6 +2151,9 @@ components:
         pipelineRunId:
           type: string
           format: uuid
+        error:
+          type: string
+          nullable: true
 
     RunResponse:
       type: object
@@ -2222,6 +2250,9 @@ components:
                 additionalProperties:
                   $ref: "#/components/schemas/MetadataValueObject"
                 nullable: true
+              error:
+                type: string
+                nullable: true
             required:
               - stepRunId
               - stepId