diff --git a/mev-boost/server/constraints.go b/mev-boost/server/constraints.go
index d6c2f6597..817ab1692 100644
--- a/mev-boost/server/constraints.go
+++ b/mev-boost/server/constraints.go
@@ -105,26 +105,34 @@ func (c *ConstraintsCache) FindTransactionByHash(txHash gethCommon.Hash) (*Trans
 	return nil, false
 }
 
-// Ref: https://docs.boltprotocol.xyz/api/builder#delegate
+// SignedDelegation represents the delegation signed by the proposer pubkey to
+// authorize the delegatee pubkey to submit constraints on their behalf.
+//
+// Specs: https://docs.boltprotocol.xyz/api/builder#delegate
 type SignedDelegation struct {
 	Message   Delegation          `json:"message"`
 	Signature phase0.BLSSignature `json:"signature"`
 }
 
-// Ref: https://docs.boltprotocol.xyz/api/builder#delegate
+// Delegation as from Specs: https://docs.boltprotocol.xyz/api/builder#delegate
 type Delegation struct {
+	Action          uint8            `json:"action"`
 	ValidatorPubkey phase0.BLSPubKey `json:"validator_pubkey"`
 	DelegateePubkey phase0.BLSPubKey `json:"delegatee_pubkey"`
 }
 
-// Ref: https://docs.boltprotocol.xyz/api/builder#revoke
+// SignedRevocation represents the revocation signed by the proposer pubkey to
+// revoke the delegatee pubkey's ability to submit constraints on their behalf.
+//
+// Specs: https://docs.boltprotocol.xyz/api/builder#revoke
 type SignedRevocation struct {
 	Message   Revocation          `json:"message"`
 	Signature phase0.BLSSignature `json:"signature"`
 }
 
-// Ref: https://docs.boltprotocol.xyz/api/builder#revoke
+// Revocation as from Specs: https://docs.boltprotocol.xyz/api/builder#revoke
 type Revocation struct {
+	Action          uint8            `json:"action"`
 	ValidatorPubkey phase0.BLSPubKey `json:"validator_pubkey"`
 	DelegateePubkey phase0.BLSPubKey `json:"delegatee_pubkey"`
 }
diff --git a/mev-boost/server/service.go b/mev-boost/server/service.go
index d0d88b6d1..746566c54 100644
--- a/mev-boost/server/service.go
+++ b/mev-boost/server/service.go
@@ -363,6 +363,10 @@ func (m *BoostService) handleDelegate(w http.ResponseWriter, req *http.Request)
 		m.respondError(w, http.StatusBadRequest, err.Error())
 		return
 	}
+	if payload.Message.Action != 0 {
+		m.respondError(w, http.StatusBadRequest, "invalid action, expected 0 for delegate")
+		return
+	}
 
 	ua := UserAgent(req.Header.Get("User-Agent"))
 	log = log.WithFields(logrus.Fields{
@@ -407,6 +411,9 @@ func (m *BoostService) handleRevoke(w http.ResponseWriter, req *http.Request) {
 		m.respondError(w, http.StatusBadRequest, err.Error())
 		return
 	}
+	if payload.Message.Action != 1 {
+		m.respondError(w, http.StatusBadRequest, "invalid action, expected 1 for revoke")
+	}
 
 	ua := UserAgent(req.Header.Get("User-Agent"))
 	log = log.WithFields(logrus.Fields{
diff --git a/mev-boost/server/service_test.go b/mev-boost/server/service_test.go
index 6efb23972..c4212951d 100644
--- a/mev-boost/server/service_test.go
+++ b/mev-boost/server/service_test.go
@@ -315,6 +315,7 @@ func TestDelegate(t *testing.T) {
 	path := pathDelegate
 	delegate := SignedDelegation{
 		Message: Delegation{
+			Action:          0,
 			ValidatorPubkey: _HexToPubkey("0xa695ad325dfc7e1191fbc9f186f58eff42a634029731b18380ff89bf42c464a42cb8ca55b200f051f57f1e1893c68759"),
 			DelegateePubkey: _HexToPubkey("0xb8ba260170b9cda2ad54c321d9a8d77e4ca34517106f587eb5ec184bf78f8a0ce4fb55658301b0dc6b129d10adf62391"),
 		},
@@ -334,6 +335,7 @@ func TestRevoke(t *testing.T) {
 	path := pathRevoke
 	revoke := SignedRevocation{
 		Message: Revocation{
+			Action:          1,
 			ValidatorPubkey: _HexToPubkey("0xa695ad325dfc7e1191fbc9f186f58eff42a634029731b18380ff89bf42c464a42cb8ca55b200f051f57f1e1893c68759"),
 			DelegateePubkey: _HexToPubkey("0xb8ba260170b9cda2ad54c321d9a8d77e4ca34517106f587eb5ec184bf78f8a0ce4fb55658301b0dc6b129d10adf62391"),
 		},