diff --git a/proto/rdf/Dockerfile b/proto/Dockerfile
similarity index 100%
rename from proto/rdf/Dockerfile
rename to proto/Dockerfile
diff --git a/proto/entrypoint.sh b/proto/entrypoint.sh
new file mode 100755
index 00000000..a48ec457
--- /dev/null
+++ b/proto/entrypoint.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+protoc --proto_path=./rdf --go_out=./rdf --go_opt=paths=source_relative --jsonschema_out=./rdf/jsonschema ./rdf/reviewdog.proto
+protoc --proto_path=./metacomment --go_out=./metacomment --go_opt=paths=source_relative ./metacomment/metacomment.proto
diff --git a/proto/metacomment/metacomment.pb.go b/proto/metacomment/metacomment.pb.go
new file mode 100644
index 00000000..2fb9b8f6
--- /dev/null
+++ b/proto/metacomment/metacomment.pb.go
@@ -0,0 +1,166 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.34.2
+// 	protoc        v5.27.1
+// source: metacomment.proto
+
+package metacomment
+
+import (
+	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
+	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	reflect "reflect"
+	sync "sync"
+)
+
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
+
+// Represents a metadata of a diagnostic result.
+// It's expected to be base64 encoded and included into reporter comments such
+// as GitHub Pull Request Review comment.
+//
+// This metadata allow reviewdog to identify the same existing comment and
+// avoid posting duplicated comments. It can also be used for resolving or
+// deleting existing comments.
+type MetaComment struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// An unique identity, or "fingerprint", of the diagnostic result.
+	Fingerprint string `protobuf:"bytes,1,opt,name=fingerprint,proto3" json:"fingerprint,omitempty"`
+	// Source (tool) name of the diagnostic result.
+	// It's important to have source name so that reviewdog can handle existing
+	// comments with the same source properly.
+	SourceName string `protobuf:"bytes,2,opt,name=source_name,json=sourceName,proto3" json:"source_name,omitempty"`
+}
+
+func (x *MetaComment) Reset() {
+	*x = MetaComment{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_metacomment_proto_msgTypes[0]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *MetaComment) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*MetaComment) ProtoMessage() {}
+
+func (x *MetaComment) ProtoReflect() protoreflect.Message {
+	mi := &file_metacomment_proto_msgTypes[0]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use MetaComment.ProtoReflect.Descriptor instead.
+func (*MetaComment) Descriptor() ([]byte, []int) {
+	return file_metacomment_proto_rawDescGZIP(), []int{0}
+}
+
+func (x *MetaComment) GetFingerprint() string {
+	if x != nil {
+		return x.Fingerprint
+	}
+	return ""
+}
+
+func (x *MetaComment) GetSourceName() string {
+	if x != nil {
+		return x.SourceName
+	}
+	return ""
+}
+
+var File_metacomment_proto protoreflect.FileDescriptor
+
+var file_metacomment_proto_rawDesc = []byte{
+	0x0a, 0x11, 0x6d, 0x65, 0x74, 0x61, 0x63, 0x6f, 0x6d, 0x6d, 0x65, 0x6e, 0x74, 0x2e, 0x70, 0x72,
+	0x6f, 0x74, 0x6f, 0x12, 0x0d, 0x72, 0x65, 0x76, 0x69, 0x65, 0x77, 0x64, 0x6f, 0x67, 0x2e, 0x72,
+	0x64, 0x66, 0x22, 0x50, 0x0a, 0x0b, 0x4d, 0x65, 0x74, 0x61, 0x43, 0x6f, 0x6d, 0x6d, 0x65, 0x6e,
+	0x74, 0x12, 0x20, 0x0a, 0x0b, 0x66, 0x69, 0x6e, 0x67, 0x65, 0x72, 0x70, 0x72, 0x69, 0x6e, 0x74,
+	0x18, 0x01, 0x20, 0x01, 0x28, 0x09, 0x52, 0x0b, 0x66, 0x69, 0x6e, 0x67, 0x65, 0x72, 0x70, 0x72,
+	0x69, 0x6e, 0x74, 0x12, 0x1f, 0x0a, 0x0b, 0x73, 0x6f, 0x75, 0x72, 0x63, 0x65, 0x5f, 0x6e, 0x61,
+	0x6d, 0x65, 0x18, 0x02, 0x20, 0x01, 0x28, 0x09, 0x52, 0x0a, 0x73, 0x6f, 0x75, 0x72, 0x63, 0x65,
+	0x4e, 0x61, 0x6d, 0x65, 0x42, 0x32, 0x5a, 0x30, 0x67, 0x69, 0x74, 0x68, 0x75, 0x62, 0x2e, 0x63,
+	0x6f, 0x6d, 0x2f, 0x72, 0x65, 0x76, 0x69, 0x65, 0x77, 0x64, 0x6f, 0x67, 0x2f, 0x72, 0x65, 0x76,
+	0x69, 0x65, 0x77, 0x64, 0x6f, 0x67, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x2f, 0x6d, 0x65, 0x74,
+	0x61, 0x63, 0x6f, 0x6d, 0x6d, 0x65, 0x6e, 0x74, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
+}
+
+var (
+	file_metacomment_proto_rawDescOnce sync.Once
+	file_metacomment_proto_rawDescData = file_metacomment_proto_rawDesc
+)
+
+func file_metacomment_proto_rawDescGZIP() []byte {
+	file_metacomment_proto_rawDescOnce.Do(func() {
+		file_metacomment_proto_rawDescData = protoimpl.X.CompressGZIP(file_metacomment_proto_rawDescData)
+	})
+	return file_metacomment_proto_rawDescData
+}
+
+var file_metacomment_proto_msgTypes = make([]protoimpl.MessageInfo, 1)
+var file_metacomment_proto_goTypes = []any{
+	(*MetaComment)(nil), // 0: reviewdog.rdf.MetaComment
+}
+var file_metacomment_proto_depIdxs = []int32{
+	0, // [0:0] is the sub-list for method output_type
+	0, // [0:0] is the sub-list for method input_type
+	0, // [0:0] is the sub-list for extension type_name
+	0, // [0:0] is the sub-list for extension extendee
+	0, // [0:0] is the sub-list for field type_name
+}
+
+func init() { file_metacomment_proto_init() }
+func file_metacomment_proto_init() {
+	if File_metacomment_proto != nil {
+		return
+	}
+	if !protoimpl.UnsafeEnabled {
+		file_metacomment_proto_msgTypes[0].Exporter = func(v any, i int) any {
+			switch v := v.(*MetaComment); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+	}
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: file_metacomment_proto_rawDesc,
+			NumEnums:      0,
+			NumMessages:   1,
+			NumExtensions: 0,
+			NumServices:   0,
+		},
+		GoTypes:           file_metacomment_proto_goTypes,
+		DependencyIndexes: file_metacomment_proto_depIdxs,
+		MessageInfos:      file_metacomment_proto_msgTypes,
+	}.Build()
+	File_metacomment_proto = out.File
+	file_metacomment_proto_rawDesc = nil
+	file_metacomment_proto_goTypes = nil
+	file_metacomment_proto_depIdxs = nil
+}
diff --git a/proto/rdf/entrypoint.sh b/proto/rdf/entrypoint.sh
deleted file mode 100755
index 9c5718ec..00000000
--- a/proto/rdf/entrypoint.sh
+++ /dev/null
@@ -1,2 +0,0 @@
-#!/bin/bash
-protoc --proto_path=. --go_out=. --go_opt=paths=source_relative --jsonschema_out=./jsonschema ./reviewdog.proto
diff --git a/proto/rdf/update.sh b/proto/update.sh
similarity index 100%
rename from proto/rdf/update.sh
rename to proto/update.sh