diff --git a/packages/cdk/lib/construct/mcp-api.ts b/packages/cdk/lib/construct/mcp-api.ts
index a24734b89..5789ceb46 100644
--- a/packages/cdk/lib/construct/mcp-api.ts
+++ b/packages/cdk/lib/construct/mcp-api.ts
@@ -1,4 +1,4 @@
-import { Duration } from 'aws-cdk-lib';
+import { Duration, Size } from 'aws-cdk-lib';
 import { Construct } from 'constructs';
 import {
   DockerImageFunction,
@@ -31,6 +31,7 @@ export class McpApi extends Construct {
           : NetworkMode.DEFAULT,
       }),
       memorySize: 1024,
+      ephemeralStorageSize: Size.mebibytes(1024),
       timeout: Duration.minutes(15),
       architecture: Architecture.X86_64,
       environment: {
diff --git a/packages/cdk/mcp-api/app.py b/packages/cdk/mcp-api/app.py
index ae25f68ef..8def7a868 100644
--- a/packages/cdk/mcp-api/app.py
+++ b/packages/cdk/mcp-api/app.py
@@ -34,6 +34,7 @@
 - You are running on AWS Lambda. Therefore, when writing files, always write them under `{WORKSPACE_DIR}`.
 - Similarly, if you need a workspace, please use the `{WORKSPACE_DIR}` directory. Do not ask the user about their current workspace. It's always `{WORKSPACE_DIR}`.
 - Also, users cannot directly access files written under `{WORKSPACE_DIR}`. So when submitting these files to users, *always upload them to S3 using the `upload_file_to_s3_and_retrieve_s3_url` tool and provide the S3 URL*. The S3 URL must be included in the final output.
+- If the output file is an image file, the S3 URL output must be in Markdown format.
 """
 
 def stream_chunk(text, trace):
@@ -168,8 +169,8 @@ def spawn():
                 command=server['command'],
                 args=server['args'],
                 env={
-                    **server['env'],
                     **UV_ENV,
+                    **server['env'],
                 },
             )
         )