diff --git a/server/schemas/internel/v1/schema.proto b/server/schemas/internel/v1/schema.proto
new file mode 100644
index 0000000000..aa35ebbeaf
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+++ b/server/schemas/internel/v1/schema.proto
@@ -0,0 +1,97 @@
+syntax = "proto3";
+
+package reearth.cms.v1;
+
+import "google/protobuf/timestamp.proto";
+
+option go_package = "proto/v1";
+
+service ReEarthCMS {
+  // Main operations
+  rpc CreateProject(CreateProjectRequest) returns (CreateProjectResponse) {}
+  rpc ListProjects(ListProjectsRequest) returns (ListProjectsResponse) {}
+  rpc ListModels(ListModelsRequest) returns (ListModelsResponse) {}
+  rpc GetModelGeoJSONExportURL(ExportRequest) returns (ExportURLResponse) {}
+}
+
+// Implementation note:
+// Authentication should be implemented using gRPC interceptors
+// M2M tokens should be passed in metadata with key "authorization"
+// Format: "Bearer <token>"
+// UserId should be passed in metadata with key "user-id"
+
+// Core messages
+message Project {
+  string id = 1;
+  string name = 2;
+  string description = 3;
+  string workspace_id = 4;
+  ProjectPublication publication = 5;
+  google.protobuf.Timestamp created_at = 6;
+  google.protobuf.Timestamp updated_at = 7;
+}
+
+message ProjectPublication {
+  ProjectPublicationScope scope = 1;
+  bool asset_public = 2;
+  optional string token = 3;
+}
+
+enum ProjectPublicationScope {
+  SCOPE_UNSPECIFIED = 0;
+  PUBLIC = 1;
+  LIMITED = 2;
+  PRIVATE = 3;
+}
+
+message Model {
+  string id = 1;
+  string project_id = 2;
+  string name = 3;
+  string description = 4;
+  string key = 5;
+  bool public = 6;
+  google.protobuf.Timestamp created_at = 7;
+  google.protobuf.Timestamp updated_at = 8;
+}
+
+// Request messages
+message CreateProjectRequest {
+  string workspace_id = 1;
+  string name = 2;
+  string description = 3;
+  string alias = 4;
+  ProjectPublication publication = 5;
+}
+
+message ListProjectsRequest {
+  string workspace_id = 1;
+}
+
+message ListModelsRequest {
+  string project_id = 1;
+}
+
+message ExportRequest {
+  string project_id = 1;
+  string model_id = 2;
+}
+
+// Response messages
+message CreateProjectResponse {
+  Project project = 1;
+}
+
+message ListProjectsResponse {
+  repeated Project projects = 1;
+  int32 total_count = 3;
+}
+
+message ListModelsResponse {
+  repeated Model models = 1;
+  int32 total_count = 3;
+}
+
+message ExportURLResponse {
+  string url = 1;
+}