diff --git a/api/server.go b/api/server.go
index 264dff5..1ad3202 100644
--- a/api/server.go
+++ b/api/server.go
@@ -28,6 +28,18 @@ type Server struct {
 	options string
 }
 
+func responseCodeToHTTP(responseCode uint32) int {
+	// Plugin should return 200 on success, 400 for caller input errors, and 500 for everything else.
+	switch responseCode {
+	case 200:
+		return http.StatusOK
+	case 400:
+		return http.StatusBadRequest
+	default:
+		return http.StatusInternalServerError
+	}
+}
+
 func NewServer(logger *zap.SugaredLogger, manager plugin.IManager, options string) *Server {
 	return &Server{
 		logger:  logger,
@@ -215,7 +227,7 @@ func (s *Server) RatsdChares(w http.ResponseWriter, r *http.Request, param Ratsd
 		if !out.Status.Result {
 			errMsg := fmt.Sprintf(
 				"failed to get attestation report from %s: %s ", pn, out.Status.Error)
-			p := problems.NewDetailedProblem(http.StatusInternalServerError, errMsg)
+			p := problems.NewDetailedProblem(responseCodeToHTTP(out.StatusCode), errMsg)
 			s.reportProblem(w, p)
 			return false
 		}
diff --git a/attesters/mocktsm/mocktsm.go b/attesters/mocktsm/mocktsm.go
index 58a658e..5da4cbd 100644
--- a/attesters/mocktsm/mocktsm.go
+++ b/attesters/mocktsm/mocktsm.go
@@ -5,6 +5,7 @@ package mocktsm
 import (
 	"encoding/json"
 	"fmt"
+	"net/http"
 	"strconv"
 
 	"github.com/google/go-configfs-tsm/configfs/configfsi"
@@ -39,11 +40,12 @@ type MockPlugin struct {
 	client *faketsm.Client
 }
 
-func getEvidenceError(e error) *compositor.EvidenceOut {
+func getEvidenceError(e error, statusCode uint32) *compositor.EvidenceOut {
 	return &compositor.EvidenceOut{
 		Status: &compositor.Status{
 			Result: false, Error: e.Error(),
 		},
+		StatusCode: statusCode,
 	}
 }
 
@@ -78,13 +80,13 @@ func (m *MockPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.Evidence
 		errMsg := fmt.Errorf(
 			"nonce size of the mockTSM attester should be %d, got %d",
 			nonceSize, uint32(len(in.Nonce)))
-		return getEvidenceError(errMsg)
+		return getEvidenceError(errMsg, http.StatusBadRequest)
 	}
 
 	if in.ContentType != mediaType {
 		errMsg := fmt.Errorf(
 			"no supported format in mock TSM plugin matches the requested format")
-		return getEvidenceError(errMsg)
+		return getEvidenceError(errMsg, http.StatusBadRequest)
 	}
 	req := &report.Request{
 		InBlob:     in.Nonce,
@@ -96,7 +98,7 @@ func (m *MockPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.Evidence
 		if err := json.Unmarshal(in.Options, &options); err != nil {
 			errMsg := fmt.Errorf(
 				"failed to parse %s: %v", in.Options, err)
-			return getEvidenceError(errMsg)
+			return getEvidenceError(errMsg, http.StatusBadRequest)
 		}
 	}
 
@@ -105,7 +107,7 @@ func (m *MockPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.Evidence
 		if err != nil || level < 0 {
 			errMsg := fmt.Errorf("privilege_level %s is invalid",
 			privlevel)
-			return getEvidenceError(errMsg)
+			return getEvidenceError(errMsg, http.StatusBadRequest)
 		}
 		req.Privilege = &report.Privilege{Level: uint(level)}
 	}
@@ -113,7 +115,7 @@ func (m *MockPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.Evidence
 	resp, err := report.Get(m.client, req)
 	if err != nil {
 		errMsg := fmt.Errorf("failed to get mock TSM report: %v", err)
-		return getEvidenceError(errMsg)
+		return getEvidenceError(errMsg, http.StatusInternalServerError)
 	}
 
 	out := &tokens.TSMReport{
@@ -125,12 +127,13 @@ func (m *MockPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.Evidence
 	outEncoded, err := out.ToJSON()
 	if err != nil {
 		errMsg := fmt.Errorf("failed to JSON encode mock TSM report: %v", err)
-		return getEvidenceError(errMsg)
+		return getEvidenceError(errMsg, http.StatusInternalServerError)
 	}
 
 	return &compositor.EvidenceOut{
 		Status:   statusSucceeded,
 		Evidence: outEncoded,
+		StatusCode: http.StatusOK,
 	}
 }
 
diff --git a/attesters/mocktsm/mocktsm_test.go b/attesters/mocktsm/mocktsm_test.go
index 59a43d5..aba28fe 100644
--- a/attesters/mocktsm/mocktsm_test.go
+++ b/attesters/mocktsm/mocktsm_test.go
@@ -5,6 +5,7 @@ package mocktsm
 import (
 	"encoding/hex"
 	"fmt"
+	"net/http"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -65,6 +66,7 @@ func Test_GetEvidence_wrong_nonce_size(t *testing.T) {
 			Result: false,
 			Error:  errMsg,
 		},
+		StatusCode: http.StatusBadRequest,
 	}
 
 	assert.Equal(t, expected, p.GetEvidence(in))
@@ -82,6 +84,7 @@ func Test_GetEvidence_invalid_format(t *testing.T) {
 			Result: false,
 			Error:  "no supported format in mock TSM plugin matches the requested format",
 		},
+		StatusCode: http.StatusBadRequest,
 	}
 
 	assert.Equal(t, expected, p.GetEvidence(in))
@@ -106,6 +109,7 @@ func Test_GetEvidence_No_Options(t *testing.T) {
 	expected := &compositor.EvidenceOut{
 		Status:   statusSucceeded,
 		Evidence: outEncoded,
+		StatusCode: http.StatusOK,
 	}
 
 	assert.Equal(t, expected, p.GetEvidence(in))
@@ -134,6 +138,7 @@ func TestGetEvidence_With_Invalid_Options(t *testing.T) {
 					Result: false,
 					Error:  tt.msg,
 				},
+				StatusCode: http.StatusBadRequest,
 			}
 
 			assert.Equal(t, expected, p.GetEvidence(in))
@@ -161,6 +166,7 @@ func Test_GetEvidence_With_Valid_Privilege_level(t *testing.T) {
 	expected := &compositor.EvidenceOut{
 		Status:   statusSucceeded,
 		Evidence: outEncoded,
+		StatusCode: http.StatusOK,
 	}
 
 	assert.Equal(t, expected, p.GetEvidence(in))
diff --git a/attesters/tsm/tsm.go b/attesters/tsm/tsm.go
index 65f6d1e..0a73b4e 100644
--- a/attesters/tsm/tsm.go
+++ b/attesters/tsm/tsm.go
@@ -5,6 +5,7 @@ package tsm
 import (
 	"encoding/json"
 	"fmt"
+	"net/http"
 	"strconv"
 
 	"github.com/google/go-configfs-tsm/configfs/linuxtsm"
@@ -41,11 +42,12 @@ var (
 
 type TSMPlugin struct{}
 
-func getEvidenceError(e error) *compositor.EvidenceOut {
+func getEvidenceError(e error, statusCode uint32) *compositor.EvidenceOut {
 	return &compositor.EvidenceOut{
 		Status: &compositor.Status{
 			Result: false, Error: e.Error(),
 		},
+		StatusCode: statusCode,
 	}
 }
 
@@ -88,7 +90,7 @@ func (t *TSMPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.EvidenceO
 		errMsg := fmt.Errorf(
 			"nonce size of the TSM attester should be %d, got %d",
 			tsmNonceSize, uint32(len(in.Nonce)))
-		return getEvidenceError(errMsg)
+		return getEvidenceError(errMsg, http.StatusBadRequest)
 	}
 
 	for _, format := range supportedFormats {
@@ -103,7 +105,7 @@ func (t *TSMPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.EvidenceO
 				if err := json.Unmarshal(in.Options, &options); err != nil {
 					errMsg := fmt.Errorf(
 						"failed to parse %s: %v", in.Options, err)
-					return getEvidenceError(errMsg)
+					return getEvidenceError(errMsg, http.StatusBadRequest)
 				}
 			}
 
@@ -112,7 +114,7 @@ func (t *TSMPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.EvidenceO
 				if err != nil || level < 0 {
 					errMsg := fmt.Errorf("privilege_level %s is invalid",
 						privlevel)
-					return getEvidenceError(errMsg)
+					return getEvidenceError(errMsg, http.StatusBadRequest)
 				}
 				req.Privilege = &report.Privilege{Level: uint(level)}
 			}
@@ -120,13 +122,13 @@ func (t *TSMPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.EvidenceO
 			client, err := linuxtsm.MakeClient()
 			if err != nil {
 				errMsg := fmt.Errorf("failed to create config TSM client: %v", err)
-				return getEvidenceError(errMsg)
+				return getEvidenceError(errMsg, http.StatusInternalServerError)
 			}
 
 			resp, err := report.Get(client, req)
 			if err != nil {
 				errMsg := fmt.Errorf("failed to get TSM report: %v", err)
-				return getEvidenceError(errMsg)
+				return getEvidenceError(errMsg, http.StatusInternalServerError)
 			}
 
 			out := &tokens.TSMReport{
@@ -148,16 +150,17 @@ func (t *TSMPlugin) GetEvidence(in *compositor.EvidenceIn) *compositor.EvidenceO
 			outEncoded, err := encodeOp()
 			if err != nil {
 				errMsg := fmt.Errorf("failed to encode TSM report as %s: %v", encodeAs, err)
-				return getEvidenceError(errMsg)
+				return getEvidenceError(errMsg, http.StatusInternalServerError)
 			}
 
 			return &compositor.EvidenceOut{
 				Status:   statusSucceeded,
 				Evidence: outEncoded,
+				StatusCode: http.StatusOK,
 			}
 		}
 	}
 
 	errMsg := fmt.Errorf("no supported format in tsm plugin matches the requested format")
-	return getEvidenceError(errMsg)
+	return getEvidenceError(errMsg, http.StatusBadRequest)
 }
diff --git a/attesters/tsm/tsm_test.go b/attesters/tsm/tsm_test.go
index 98efe79..cbea6f1 100644
--- a/attesters/tsm/tsm_test.go
+++ b/attesters/tsm/tsm_test.go
@@ -4,6 +4,7 @@ package tsm
 
 import (
 	"fmt"
+	"net/http"
 	"testing"
 
 	"github.com/google/go-configfs-tsm/configfs/linuxtsm"
@@ -20,15 +21,19 @@ var (
 )
 
 func Test_getEvidenceError(t *testing.T) {
-	e := fmt.Errorf("sample error")
+	tests := []uint32 {http.StatusBadRequest, http.StatusBadRequest}
+	for _, tt := range tests {
+		e := fmt.Errorf("sample error")
 
-	expected := &compositor.EvidenceOut{
-		Status: &compositor.Status{
-			Result: false, Error: "sample error",
-		},
-	}
+		expected := &compositor.EvidenceOut{
+			Status: &compositor.Status{
+				Result: false, Error: "sample error",
+			},
+			StatusCode: tt,
+		}
 
-	assert.Equal(t, expected, getEvidenceError(e))
+		assert.Equal(t, expected, getEvidenceError(e, tt))
+	}
 }
 
 func Test_GetOptions(t *testing.T) {
@@ -87,6 +92,7 @@ func Test_GetEvidence_wrong_nonce_size(t *testing.T) {
 			Result: false,
 			Error:  errMsg,
 		},
+		StatusCode: http.StatusBadRequest,
 	}
 
 	assert.Equal(t, expected, p.GetEvidence(in))
@@ -104,6 +110,7 @@ func Test_GetEvidence_invalid_format(t *testing.T) {
 			Result: false,
 			Error:  "no supported format in tsm plugin matches the requested format",
 		},
+		StatusCode: http.StatusBadRequest,
 	}
 
 	assert.Equal(t, expected, p.GetEvidence(in))
@@ -133,6 +140,7 @@ func TestGetEvidence_With_Invalid_Options(t *testing.T) {
 					Result: false,
 					Error:  tt.msg,
 				},
+				StatusCode: http.StatusBadRequest,
 			}
 
 			assert.Equal(t, expected, p.GetEvidence(in))
diff --git a/proto/compositor.proto b/proto/compositor.proto
index 5fdd576..ccc5606 100644
--- a/proto/compositor.proto
+++ b/proto/compositor.proto
@@ -60,5 +60,6 @@ message EvidenceIn {
 
 message EvidenceOut {
   Status status = 1;
-  bytes evidence = 2;
+  uint32 statusCode = 2;
+  bytes evidence = 3;
 }
diff --git a/proto/compositor/compositor.pb.go b/proto/compositor/compositor.pb.go
index 4e7ee2e..63ee48d 100644
--- a/proto/compositor/compositor.pb.go
+++ b/proto/compositor/compositor.pb.go
@@ -478,8 +478,9 @@ type EvidenceOut struct {
 	sizeCache     protoimpl.SizeCache
 	unknownFields protoimpl.UnknownFields
 
-	Status   *Status `protobuf:"bytes,1,opt,name=status,proto3" json:"status,omitempty"`
-	Evidence []byte  `protobuf:"bytes,2,opt,name=evidence,proto3" json:"evidence,omitempty"`
+	Status     *Status `protobuf:"bytes,1,opt,name=status,proto3" json:"status,omitempty"`
+	StatusCode uint32  `protobuf:"varint,2,opt,name=statusCode,proto3" json:"statusCode,omitempty"`
+	Evidence   []byte  `protobuf:"bytes,3,opt,name=evidence,proto3" json:"evidence,omitempty"`
 }
 
 func (x *EvidenceOut) Reset() {
@@ -521,6 +522,13 @@ func (x *EvidenceOut) GetStatus() *Status {
 	return nil
 }
 
+func (x *EvidenceOut) GetStatusCode() uint32 {
+	if x != nil {
+		return x.StatusCode
+	}
+	return 0
+}
+
 func (x *EvidenceOut) GetEvidence() []byte {
 	if x != nil {
 		return x.Evidence
@@ -577,12 +585,14 @@ var file_compositor_proto_rawDesc = []byte{
 	0x74, 0x65, 0x6e, 0x74, 0x54, 0x79, 0x70, 0x65, 0x12, 0x14, 0x0a, 0x05, 0x6e, 0x6f, 0x6e, 0x63,
 	0x65, 0x18, 0x02, 0x20, 0x01, 0x28, 0x0c, 0x52, 0x05, 0x6e, 0x6f, 0x6e, 0x63, 0x65, 0x12, 0x18,
 	0x0a, 0x07, 0x6f, 0x70, 0x74, 0x69, 0x6f, 0x6e, 0x73, 0x18, 0x03, 0x20, 0x01, 0x28, 0x0c, 0x52,
-	0x07, 0x6f, 0x70, 0x74, 0x69, 0x6f, 0x6e, 0x73, 0x22, 0x55, 0x0a, 0x0b, 0x45, 0x76, 0x69, 0x64,
+	0x07, 0x6f, 0x70, 0x74, 0x69, 0x6f, 0x6e, 0x73, 0x22, 0x75, 0x0a, 0x0b, 0x45, 0x76, 0x69, 0x64,
 	0x65, 0x6e, 0x63, 0x65, 0x4f, 0x75, 0x74, 0x12, 0x2a, 0x0a, 0x06, 0x73, 0x74, 0x61, 0x74, 0x75,
 	0x73, 0x18, 0x01, 0x20, 0x01, 0x28, 0x0b, 0x32, 0x12, 0x2e, 0x63, 0x6f, 0x6d, 0x70, 0x6f, 0x73,
 	0x69, 0x74, 0x6f, 0x72, 0x2e, 0x53, 0x74, 0x61, 0x74, 0x75, 0x73, 0x52, 0x06, 0x73, 0x74, 0x61,
-	0x74, 0x75, 0x73, 0x12, 0x1a, 0x0a, 0x08, 0x65, 0x76, 0x69, 0x64, 0x65, 0x6e, 0x63, 0x65, 0x18,
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+	0x74, 0x75, 0x73, 0x12, 0x1e, 0x0a, 0x0a, 0x73, 0x74, 0x61, 0x74, 0x75, 0x73, 0x43, 0x6f, 0x64,
+	0x65, 0x18, 0x02, 0x20, 0x01, 0x28, 0x0d, 0x52, 0x0a, 0x73, 0x74, 0x61, 0x74, 0x75, 0x73, 0x43,
+	0x6f, 0x64, 0x65, 0x12, 0x1a, 0x0a, 0x08, 0x65, 0x76, 0x69, 0x64, 0x65, 0x6e, 0x63, 0x65, 0x18,
+	0x03, 0x20, 0x01, 0x28, 0x0c, 0x52, 0x08, 0x65, 0x76, 0x69, 0x64, 0x65, 0x6e, 0x63, 0x65, 0x32,
 	0xa4, 0x02, 0x0a, 0x0a, 0x43, 0x6f, 0x6d, 0x70, 0x6f, 0x73, 0x69, 0x74, 0x6f, 0x72, 0x12, 0x3c,
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