diff --git a/polygerrit-ui/app/api/admin.ts b/polygerrit-ui/app/api/admin.ts
index a7b549d..0606153 100644
--- a/polygerrit-ui/app/api/admin.ts
+++ b/polygerrit-ui/app/api/admin.ts
@@ -16,13 +16,13 @@
  */
 
 /** Interface for menu link */
-export interface MenuLink {
+export declare interface MenuLink {
   text: string;
   url: string;
   capability: string | null;
 }
 
-export interface AdminPluginApi {
+export declare interface AdminPluginApi {
   addMenuLink(text: string, url: string, capability?: string): void;
 
   getMenuLinks(): MenuLink[];
diff --git a/polygerrit-ui/app/api/annotation.ts b/polygerrit-ui/app/api/annotation.ts
index bd4f399..ad0846d 100644
--- a/polygerrit-ui/app/api/annotation.ts
+++ b/polygerrit-ui/app/api/annotation.ts
@@ -36,7 +36,7 @@
   change?: unknown
 ) => Promise<Array<CoverageRange>>;
 
-export interface AnnotationPluginApi {
+export declare interface AnnotationPluginApi {
   /**
    * The specified function will be called when a gr-diff component is built,
    * and feeds the returned coverage data into the diff. Optional.
diff --git a/polygerrit-ui/app/api/attribute-helper.ts b/polygerrit-ui/app/api/attribute-helper.ts
index cd52259..d813beb 100644
--- a/polygerrit-ui/app/api/attribute-helper.ts
+++ b/polygerrit-ui/app/api/attribute-helper.ts
@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-export interface AttributeHelperPluginApi {
+export declare interface AttributeHelperPluginApi {
   /**
    * Binds callback to property updates.
    *
diff --git a/polygerrit-ui/app/api/change-actions.ts b/polygerrit-ui/app/api/change-actions.ts
index 8638295..2ce697a 100644
--- a/polygerrit-ui/app/api/change-actions.ts
+++ b/polygerrit-ui/app/api/change-actions.ts
@@ -16,7 +16,7 @@
  */
 import {HttpMethod} from './rest';
 
-export interface ActionInfo {
+export declare interface ActionInfo {
   method?: HttpMethod;
   label?: string;
   title?: string;
@@ -71,7 +71,7 @@
 
 export type PrimaryActionKey = ChangeActions | RevisionActions;
 
-export interface ChangeActionsPluginApi {
+export declare interface ChangeActionsPluginApi {
   addPrimaryActionKey(key: PrimaryActionKey): void;
 
   removePrimaryActionKey(key: string): void;
diff --git a/polygerrit-ui/app/api/change-reply.ts b/polygerrit-ui/app/api/change-reply.ts
index 6016004..bcbdc61 100644
--- a/polygerrit-ui/app/api/change-reply.ts
+++ b/polygerrit-ui/app/api/change-reply.ts
@@ -14,17 +14,17 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-export interface LabelsChangedDetail {
+export declare interface LabelsChangedDetail {
   name: string;
   value: string;
 }
-export interface ValueChangedDetail {
+export declare interface ValueChangedDetail {
   value: string;
 }
 export type ReplyChangedCallback = (text: string) => void;
 export type LabelsChangedCallback = (detail: LabelsChangedDetail) => void;
 
-export interface ChangeReplyPluginApi {
+export declare interface ChangeReplyPluginApi {
   getLabelValue(label: string): string;
 
   setLabelValue(label: string, value: string): void;
diff --git a/polygerrit-ui/app/api/checks.ts b/polygerrit-ui/app/api/checks.ts
index ee4ea9e..62b9ad9 100644
--- a/polygerrit-ui/app/api/checks.ts
+++ b/polygerrit-ui/app/api/checks.ts
@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-export interface ChecksPluginApi {
+export declare interface ChecksPluginApi {
   /**
    * Must only be called once. You cannot register twice. You cannot unregister.
    */
@@ -29,7 +29,7 @@
   announceUpdate(): void;
 }
 
-export interface ChecksApiConfig {
+export declare interface ChecksApiConfig {
   /**
    * How often should the provider be called for new CheckData while the user
    * navigates change related pages and the browser tab remains visible?
@@ -38,7 +38,7 @@
   fetchPollingIntervalSeconds: number;
 }
 
-export interface ChangeData {
+export declare interface ChangeData {
   changeNumber: number;
   patchsetNumber: number;
   patchsetSha: string;
@@ -48,7 +48,7 @@
   changeInfo: unknown;
 }
 
-export interface ChecksProvider {
+export declare interface ChecksProvider {
   /**
    * Gerrit calls this method when ...
    * - ... the change or diff page is loaded.
@@ -59,7 +59,7 @@
   fetch(change: ChangeData): Promise<FetchResponse>;
 }
 
-export interface FetchResponse {
+export declare interface FetchResponse {
   responseCode: ResponseCode;
 
   /** Only relevant when the responseCode is ERROR. */
@@ -102,7 +102,7 @@
  * runs are completed the users' interest shifts to results: What do I have to
  * fix? The only actions that can be associated with runs are RUN and CANCEL.
  */
-export interface CheckRun {
+export declare interface CheckRun {
   /**
    * Gerrit requests check runs and results from the plugin by change number and
    * patchset number. So these two properties can as well be left empty when
@@ -221,7 +221,7 @@
   results?: CheckResult[];
 }
 
-export interface Action {
+export declare interface Action {
   name: string;
   tooltip?: string;
   /**
@@ -272,7 +272,7 @@
  * If `message` is empty or undefined, then the `Triggering ...` toast will just
  * be hidden and no further toast will be shown.
  */
-export interface ActionResult {
+export declare interface ActionResult {
   /** An empty errorMessage means success. */
   message?: string;
   /**
@@ -290,7 +290,7 @@
   COMPLETED = 'COMPLETED',
 }
 
-export interface CheckResult {
+export declare interface CheckResult {
   /**
    * An optional opaque identifier not used by Gerrit directly, but might be
    * used by plugin extensions and callbacks.
@@ -388,7 +388,7 @@
   ERROR = 'ERROR',
 }
 
-export interface Tag {
+export declare interface Tag {
   name: string;
   tooltip?: string;
   color?: TagColor;
@@ -404,7 +404,7 @@
   BROWN = 'brown',
 }
 
-export interface Link {
+export declare interface Link {
   /** Must begin with 'http'. */
   url: string;
   tooltip?: string;
diff --git a/polygerrit-ui/app/api/diff.ts b/polygerrit-ui/app/api/diff.ts
index 360ff5c..6e142d4 100644
--- a/polygerrit-ui/app/api/diff.ts
+++ b/polygerrit-ui/app/api/diff.ts
@@ -55,7 +55,7 @@
 /**
  * Represents a syntax block in a code (e.g. method, function, class, if-else).
  */
-export interface SyntaxBlock {
+export declare interface SyntaxBlock {
   /** Name of the block (e.g. name of the method/class)*/
   name: string;
   /** Where does this block syntatically starts and ends (line number and column).*/
diff --git a/polygerrit-ui/app/api/event-helper.ts b/polygerrit-ui/app/api/event-helper.ts
index 16c327d..5dc15dc 100644
--- a/polygerrit-ui/app/api/event-helper.ts
+++ b/polygerrit-ui/app/api/event-helper.ts
@@ -16,7 +16,7 @@
  */
 export type UnsubscribeCallback = () => void;
 
-export interface EventHelperPluginApi {
+export declare interface EventHelperPluginApi {
   /**
    * Alias for @see onClick
    */
diff --git a/polygerrit-ui/app/api/hook.ts b/polygerrit-ui/app/api/hook.ts
index 179b967..0ac6468 100644
--- a/polygerrit-ui/app/api/hook.ts
+++ b/polygerrit-ui/app/api/hook.ts
@@ -30,12 +30,12 @@
 
 export type HookCallback = (el: HTMLElement & GerritElementExtensions) => void;
 
-export interface RegisterOptions {
+export declare interface RegisterOptions {
   slot?: string;
   replace: unknown;
 }
 
-export interface HookApi {
+export declare interface HookApi {
   onAttached(callback: HookCallback): HookApi;
 
   onDetached(callback: HookCallback): HookApi;
diff --git a/polygerrit-ui/app/api/plugin.ts b/polygerrit-ui/app/api/plugin.ts
index 0aadb38..0c91546 100644
--- a/polygerrit-ui/app/api/plugin.ts
+++ b/polygerrit-ui/app/api/plugin.ts
@@ -48,7 +48,7 @@
   HIGHLIGHTJS_LOADED = 'highlightjs-loaded',
 }
 
-export interface PluginApi {
+export declare interface PluginApi {
   _url?: URL;
   admin(): AdminPluginApi;
   annotationApi(): AnnotationPluginApi;
diff --git a/polygerrit-ui/app/api/popup.ts b/polygerrit-ui/app/api/popup.ts
index 60772cc..8d81831 100644
--- a/polygerrit-ui/app/api/popup.ts
+++ b/polygerrit-ui/app/api/popup.ts
@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-export interface PopupPluginApi {
+export declare interface PopupPluginApi {
   /**
    * Opens the popup, inserts it into DOM over current UI.
    * Creates the popup if not previously created. Creates popup content element,
diff --git a/polygerrit-ui/app/api/reporting.ts b/polygerrit-ui/app/api/reporting.ts
index 65bdc3f..c3655bb 100644
--- a/polygerrit-ui/app/api/reporting.ts
+++ b/polygerrit-ui/app/api/reporting.ts
@@ -18,7 +18,7 @@
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 export type EventDetails = any;
 
-export interface ReportingPluginApi {
+export declare interface ReportingPluginApi {
   reportInteraction(eventName: string, details?: EventDetails): void;
 
   reportLifeCycle(eventName: string, details?: EventDetails): void;
diff --git a/polygerrit-ui/app/api/rest.ts b/polygerrit-ui/app/api/rest.ts
index fd9cada..2b91bf6 100644
--- a/polygerrit-ui/app/api/rest.ts
+++ b/polygerrit-ui/app/api/rest.ts
@@ -26,7 +26,7 @@
 
 export type ErrorCallback = (response?: Response | null, err?: Error) => void;
 
-export interface RestPluginApi {
+export declare interface RestPluginApi {
   getLoggedIn(): Promise<boolean>;
 
   getVersion(): Promise<string | undefined>;