diff --git a/shared/transactions/credential_accept.yaml b/shared/transactions/credential_accept.yaml
index 87a2df6..3886353 100644
--- a/shared/transactions/credential_accept.yaml
+++ b/shared/transactions/credential_accept.yaml
@@ -13,10 +13,14 @@ components:
       properties:
         CredentialType:
           type: string
+          pattern: '^[0-9a-fA-F]+$'
           description: Arbitrary data defining the type of credential. The minimum size is 1 byte and the maximum is 64 bytes.
         Issuer:
           type: string
           description: The address of the issuer that created the credential.
+      x-custom-validation:
+        validCredentialType:
+          field: CredentialType
 
     CredentialAcceptErrorCode:
       $id: CredentialAcceptErrorCode
diff --git a/shared/transactions/credential_create.yaml b/shared/transactions/credential_create.yaml
index 9181684..6dc945c 100644
--- a/shared/transactions/credential_create.yaml
+++ b/shared/transactions/credential_create.yaml
@@ -16,6 +16,7 @@ components:
       properties:
         CredentialType:
           type: string
+          pattern: '^[0-9a-fA-F]+$'
           description: Arbitrary data defining the type of credential this entry represents. The minimum length is 1 byte and the maximum length is 64 bytes.
         Expiration:
           type: number
@@ -26,9 +27,14 @@ components:
           description: The subject of the credential.
         URI:
           type: string
+          pattern: '^[0-9a-fA-F]+$'
+          maxLength: 512
           description: |
             Arbitrary additional data about the credential, such as the URL where users can look up an associated Verifiable Credential document. 
             If present, the minimum length is 1 byte and the maximum is 256 bytes.
+      x-custom-validation:
+        validCredentialType:
+          field: CredentialType
 
     CredentialCreateErrorCode:
       $id: CredentialCreateErrorCode
diff --git a/shared/transactions/credential_delete.yaml b/shared/transactions/credential_delete.yaml
index 8414566..a278024 100644
--- a/shared/transactions/credential_delete.yaml
+++ b/shared/transactions/credential_delete.yaml
@@ -13,6 +13,7 @@ components:
       properties:
         CredentialType:
           type: string
+          pattern: '^[0-9a-fA-F]+$'
           description: Arbitrary data defining the type of credential to delete. The minimum length is 1 byte and the maximum length is 256 bytes.
         Subject:
           type: string
@@ -25,6 +26,8 @@ components:
           - fields:
               - Subject
               - Issuer
+        validCredentialType:
+          field: CredentialType
 
     CredentialDeleteErrorCode:
       $id: CredentialDeleteErrorCode