diff --git a/src/folksonomy.ts b/src/folksonomy.ts
index 005007d..74e9c34 100644
--- a/src/folksonomy.ts
+++ b/src/folksonomy.ts
@@ -15,10 +15,12 @@ export type FolksonomyKey = {
 export class Folksonomy {
   private readonly fetch: typeof global.fetch;
   private readonly baseUrl: string;
+  private authToken?: string;
   readonly raw: ReturnType<typeof createClient<paths>>;
 
-  constructor(fetch: typeof global.fetch, authToken: string) {
+  constructor(fetch: typeof global.fetch, authToken?: string) {
     this.baseUrl = "https://api.folksonomy.openfoodfacts.org";
+    this.authToken = authToken;
 
     this.fetch = fetch;
     this.raw = createClient({
@@ -32,6 +34,14 @@ export class Folksonomy {
     });
   }
 
+  private validateAuthToken(message?: string) {
+    if (!this.authToken) {
+      throw new Error(
+        message || "Auth token is required to perform this action",
+      );
+    }
+  }
+
   /**
    * Get the list of keys with statistics
    *
@@ -53,6 +63,8 @@ export class Folksonomy {
   }
 
   async putTag(tag: FolksonomyTag): Promise<boolean> {
+    this.validateAuthToken();
+
     const res = await this.raw.PUT("/product", { body: tag });
 
     return res.response.status === 200;
@@ -81,6 +93,8 @@ export class Folksonomy {
    * @returns if the tag was added or updated
    */
   async addTag(tag: FolksonomyTag): Promise<boolean> {
+    this.validateAuthToken();
+
     const res = await this.raw.POST("/product", {
       body: tag,
     });
@@ -94,6 +108,8 @@ export class Folksonomy {
    * @returns if the tag was deleted
    */
   async removeTag(tag: FolksonomyTag & { version: number }) {
+    this.validateAuthToken();
+
     const res = await this.raw.DELETE("/product/{product}/{k}", {
       params: {
         path: { product: tag.product, k: tag.k },