diff --git a/src/proxy/transformers/request-transformer.ts b/src/proxy/transformers/request-transformer.ts
index 2f447fee..0942244e 100644
--- a/src/proxy/transformers/request-transformer.ts
+++ b/src/proxy/transformers/request-transformer.ts
@@ -224,8 +224,8 @@ function convertToolResultContent(content: unknown, isError: boolean, label: str
           ? (parsed.source as Record<string, unknown>)
           : undefined;
       const description =
-        source?.type === 'url' && typeof source.url === 'string'
-          ? source.url
+        source?.type === 'url'
+          ? 'url image payload'
           : source?.type === 'base64' && typeof source.media_type === 'string'
             ? `${source.media_type} base64 payload`
             : 'unsupported image payload';
diff --git a/tests/unit/proxy/transformers/request-transformer-regressions.test.ts b/tests/unit/proxy/transformers/request-transformer-regressions.test.ts
index c34798bd..79ceba27 100644
--- a/tests/unit/proxy/transformers/request-transformer-regressions.test.ts
+++ b/tests/unit/proxy/transformers/request-transformer-regressions.test.ts
@@ -220,7 +220,7 @@ describe('ProxyRequestTransformer regressions', () => {
       role: 'tool',
       tool_call_id: 'toolu_1',
       content:
-        'screenshot captured\n[tool_result image omitted: https://example.com/error.png]\n[tool_result image omitted: image/png base64 payload]',
+        'screenshot captured\n[tool_result image omitted: url image payload]\n[tool_result image omitted: image/png base64 payload]',
     });
   });