diff --git a/src/audio/interfaces.ts b/src/audio/interfaces.ts
index 7b211c1..128cf18 100644
--- a/src/audio/interfaces.ts
+++ b/src/audio/interfaces.ts
@@ -3,7 +3,7 @@ import { BaseResponse } from "../../types";
 export interface SpeechToTextParams {
   url?: string;
   file_store_key?: string;
-  language?: string;
+  language?: LanguageCodes | "auto";
   translate?: boolean;
   by_speaker?: boolean;
   webhook_url?: string;
@@ -31,3 +31,167 @@ export interface SpeechToTextWebhookResponse extends BaseResponse {
   status: "processing" | "error";
   id: string;
 }
+
+export type LanguageCodes =
+  | "af"
+  | "am"
+  | "ar"
+  | "as"
+  | "az"
+  | "ba"
+  | "be"
+  | "bg"
+  | "bn"
+  | "bo"
+  | "br"
+  | "bs"
+  | "ca"
+  | "ch"
+  | "co"
+  | "cs"
+  | "cy"
+  | "da"
+  | "de"
+  | "dv"
+  | "dz"
+  | "el"
+  | "en"
+  | "eo"
+  | "es"
+  | "et"
+  | "eu"
+  | "fa"
+  | "ff"
+  | "fi"
+  | "fj"
+  | "fo"
+  | "fr"
+  | "fy"
+  | "ga"
+  | "gd"
+  | "gl"
+  | "gu"
+  | "gv"
+  | "ha"
+  | "he"
+  | "hi"
+  | "hr"
+  | "ht"
+  | "hu"
+  | "hy"
+  | "id"
+  | "ig"
+  | "is"
+  | "it"
+  | "iu"
+  | "ja"
+  | "jv"
+  | "ka"
+  | "kg"
+  | "ki"
+  | "kj"
+  | "kk"
+  | "kl"
+  | "km"
+  | "kn"
+  | "ko"
+  | "kr"
+  | "ks"
+  | "ku"
+  | "kv"
+  | "kw"
+  | "ky"
+  | "la"
+  | "lb"
+  | "lg"
+  | "li"
+  | "ln"
+  | "lo"
+  | "lt"
+  | "lu"
+  | "lv"
+  | "mg"
+  | "mh"
+  | "mi"
+  | "mk"
+  | "ml"
+  | "mn"
+  | "mo"
+  | "mr"
+  | "ms"
+  | "mt"
+  | "my"
+  | "na"
+  | "nb"
+  | "nd"
+  | "ne"
+  | "ng"
+  | "nl"
+  | "nn"
+  | "no"
+  | "nr"
+  | "nv"
+  | "ny"
+  | "oc"
+  | "oj"
+  | "om"
+  | "or"
+  | "os"
+  | "pa"
+  | "pi"
+  | "pl"
+  | "ps"
+  | "pt"
+  | "qu"
+  | "rm"
+  | "rn"
+  | "ro"
+  | "ru"
+  | "rw"
+  | "sa"
+  | "sc"
+  | "sd"
+  | "se"
+  | "sg"
+  | "sh"
+  | "si"
+  | "sk"
+  | "sl"
+  | "sm"
+  | "sn"
+  | "so"
+  | "sq"
+  | "sr"
+  | "ss"
+  | "st"
+  | "su"
+  | "sv"
+  | "sw"
+  | "ta"
+  | "te"
+  | "tg"
+  | "th"
+  | "ti"
+  | "tk"
+  | "tl"
+  | "tn"
+  | "to"
+  | "tr"
+  | "ts"
+  | "tt"
+  | "tw"
+  | "ty"
+  | "ug"
+  | "uk"
+  | "ur"
+  | "uz"
+  | "ve"
+  | "vi"
+  | "vo"
+  | "wo"
+  | "xh"
+  | "yi"
+  | "yo"
+  | "zh"
+  | "zh-TW"
+  | "zu";
diff --git a/src/vercel-ai-toolkit.ts b/src/vercel-ai-toolkit.ts
index 13a64ae..cd03e16 100644
--- a/src/vercel-ai-toolkit.ts
+++ b/src/vercel-ai-toolkit.ts
@@ -1,5 +1,6 @@
 import { z } from "zod";
 import { BaseConfig } from "../types";
+import { LanguageCodes } from "./audio/interfaces";
 import { JigsawStack } from "./core";
 import { tool } from "./vercel-tool";
 
@@ -283,7 +284,7 @@ export class JigsawStackToolSet {
           return await this.jigsawStack.audio.speech_to_text({
             url,
             file_store_key,
-            language,
+            language: language as LanguageCodes | "auto",
             translate,
             by_speaker,
           });
diff --git a/tests/audio.test.ts b/tests/audio.test.ts
index 94a4fec..7a0aba7 100644
--- a/tests/audio.test.ts
+++ b/tests/audio.test.ts
@@ -66,4 +66,25 @@ describe("STT APIs", () => {
     expectProperty(result, "text");
     expectType(result.text, "string");
   });
+
+  test("speech to text with auto language", async () => {
+    const result = await client.audio.speech_to_text({
+      url: audioUrl,
+      language: "auto",
+    });
+
+    expectSuccess(result);
+    expectProperty(result, "text");
+    expectType(result.text, "string");
+  });
+
+  test("speech to text with invalid language", async () => {
+    const result = await client.audio.speech_to_text({
+      url: audioUrl,
+    });
+
+    expectSuccess(result);
+    expectProperty(result, "text");
+    expectType(result.text, "string");
+  });
 });
diff --git a/tests/vision.test.ts b/tests/vision.test.ts
index 5cba11c..afaf537 100644
--- a/tests/vision.test.ts
+++ b/tests/vision.test.ts
@@ -2,10 +2,9 @@ import { beforeEach, describe, test } from "node:test";
 import { createJigsawStackClient, expectArray, expectProperty, expectSuccess, expectType } from "./test-helpers.js";
 
 const TEST_URLS = {
-  image: "https://upload.wikimedia.org/wikipedia/commons/thumb/4/47/PNG_transparency_demonstration_1.png/280px-PNG_transparency_demonstration_1.png",
+  image: "https://jigsawstack.com/preview/object-detection-example-input.jpg",
   pdf: "https://www.w3.org/WAI/WCAG21/working-examples/pdf-table/table.pdf",
   textImage: "https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Vd-Orig.png/256px-Vd-Orig.png",
-  receipt: "https://jigsawstack.com/preview/receipt-example.jpg", // Example receipt image
 };
 
 // Comprehensive VOCR API Tests