MCP server returns success logs but no response in Python (LangChain) chatbot

[Aaron-Bae]

Hello,

(This post was translated from Korean using GPT, so there may be slight wording inaccuracies — apologies in advance.)

I am using the following MCP server to query AWS resources through a Slack-based chatbot:
👉 https://github.com/awslabs/mcp/tree/main/src/aws-api-mcp-server

Environment: Python (LangChain)-based chatbot

Behavior:

When the chatbot asks, e.g., "Show me the list of EC2 instances", the MCP server (Docker) successfully executes the AWS CLI command.

The server logs a 200 response with the expected AWS resource data.

However, the chatbot never receives the response, and instead times out.

Timeout configuration: Even when I set the timeout to 30 minutes, no response ever arrives in the chatbot.

Important note: When I run the exact same MCP module inside Cursor IDE, everything works fine. The MCP settings are identical in both Cursor IDE and my chatbot app.

Here is my MCP configuration:

"aws-api": { "command": "docker", "args": [ "run", "--rm", "--interactive", "--env", "AWS_REGION=ap-northeast-2", "--volume", "C:\\Users\\User\\.aws:/app/.aws", "public.ecr.aws/awslabs-mcp/awslabs/aws-api-mcp-server:latest" ], "enabled": true, "description": "AWS API Integration" }

| INFO | awslabs.aws_api_mcp_server.core.aws.service:_log_successful_execution:215 - AWS CLI command executed successfully: { "Reservations": [ { "ReservationId": "r-************", "Instances": [ { "InstanceId": "i-************", "PrivateIpAddress": "100.4.10.117", "SecurityGroups": [ {"GroupId": "sg-************", "GroupName": "mzcsg-dummy-dev"} ], "Tags": [{"Key": "Name", "Value": "mzcec2-aps-model"}], "State": {"Name": "running"} ... } ] } ] }

Despite this successful execution log, the chatbot process never gets a response back from the MCP server.

Has anyone run into a similar issue?

Why would it work fine inside Cursor IDE but fail with timeout in a Python (LangChain) application?

Could this be related to stdio handling between Docker and the chatbot app?

Any guidance or suggestions would be greatly appreciated. Thanks in advance! 🙏

[Aaron-Bae]

When I use the exact same code but only change the MCP server image from

public.ecr.aws/awslabs-mcp/awslabs/aws-api-mcp-server:latest

to

acuvity/mcp-server-aws-ecs:latest

the chatbot works fine and receives the responses correctly.

However, my goal is to manage all AWS resources, not just ECS, so I specifically need the aws-api-mcp-server.