diff --git a/proto/caosdb/file_transmission/v1alpha1/file_transmission.proto b/proto/caosdb/file_transmission/v1alpha1/file_transmission.proto
index e82dfbc2d60db7bc344d7e507505a85328c10055..7dd80cc6b8ff3b8e9c690c50efbbe89b0e9f2c53 100644
--- a/proto/caosdb/file_transmission/v1alpha1/file_transmission.proto
+++ b/proto/caosdb/file_transmission/v1alpha1/file_transmission.proto
@@ -86,15 +86,23 @@ enum TransmissionStatus {
 // TODO: This is very similar to the Hash message in the entity API. We should discuss
 //       if and how they can be merged.
 enum ChecksumAlgorithm {
+  // The checksum algorithm is unspecified.
   CHECKSUM_ALGORITHM_UNSPECIFIED = 0;
+  // The MD5 checksum algorithm.
   CHECKSUM_ALGORITHM_MD5 = 1;
+  // The SHA-1 checksum algorithm.
   CHECKSUM_ALGORITHM_SHA1 = 2;
+  // The SHA-256 checksum algorithm.
   CHECKSUM_ALGORITHM_SHA256 = 3;
+  // The SHA-512 checksum algorithm.
   CHECKSUM_ALGORITHM_SHA512 = 4;
 }
 
+// Checksum contains the checksum value and the algorithm used to compute it.
 message Checksum {
+  // The checksum value.
   string checksum = 1;
+  // The algorithm used to compute the checksum.
   ChecksumAlgorithm checksum_algorithm = 2;
 }
 
@@ -116,20 +124,25 @@ message FileInformation {
 // Register a file upload for a list of files. The server will respond with a
 // registration id and URLs to which the files can be uploaded.
 message RegisterFileUploadRequest {
+  // Information about the files to be uploaded.
   repeated FileInformation file_information = 1;
 }
 
 // The URL to which a file should be uploaded using the given LinkAhead
 // UploadProtocolVersion.
 message UploadLocation {
+  // The URL to which the file should be uploaded.
   string url = 1;
 }
 
 // The version of the LinkAhead upload protocol. This is currently identical to
 // the TUS protocol version.
 message UploadProtocolVersion {
+  // The major version number of the upload protocol.
   int32 major = 1;
+  // The minor version number of the upload protocol.
   int32 minor = 2;
+  // The patch version number of the upload protocol.
   int32 patch = 3;
 }
 
@@ -142,7 +155,9 @@ message RegisterFileUploadResponse {
   string registration_id = 2;
   // The server's transmission settings for the upload.
   FileTransmissionSettings upload_settings = 4;
+  // The version of the LinkAhead upload protocol.
   UploadProtocolVersion version = 5;
+  // The locations where the files should be uploaded.
   repeated UploadLocation locations = 6;
 }