diff --git a/src/tools/look-at/mime-type-inference.test.ts b/src/tools/look-at/mime-type-inference.test.ts
index ed76e1b4..69ac6e6b 100644
--- a/src/tools/look-at/mime-type-inference.test.ts
+++ b/src/tools/look-at/mime-type-inference.test.ts
@@ -33,4 +33,9 @@ describe("mime type inference", () => {
     const base64 = extractBase64Data("data:image/png;base64,abc123")
     expect(base64).toBe("abc123")
   })
+
+  test("extracts raw base64 data from data URL with extra parameters", () => {
+    const base64 = extractBase64Data("data:image/heic;name=clip.heic;base64,abc123")
+    expect(base64).toBe("abc123")
+  })
 })
diff --git a/src/tools/look-at/tools.ts b/src/tools/look-at/tools.ts
index b7643860..a4c67f05 100644
--- a/src/tools/look-at/tools.ts
+++ b/src/tools/look-at/tools.ts
@@ -60,7 +60,7 @@ export function createLookAt(ctx: PluginInput): ToolDefinition {
           if (needsConversion(mimeType)) {
             log(`[look_at] Detected unsupported Base64 format: ${mimeType}, converting to JPEG...`)
             try {
-              const { base64, tempFiles } = convertBase64ImageToJpeg(imageData, mimeType)
+              const { base64, tempFiles } = convertBase64ImageToJpeg(finalBase64Data, mimeType)
               finalBase64Data = base64
               finalMimeType = "image/jpeg"
               tempFilesToCleanup = tempFiles