Open WebUI + OpenSearch MCP (Single Repo)

This repository starts everything with one Docker Compose command:

• OpenSearch: http://localhost:9200
• OpenSearch Dashboards: http://localhost:5601
• MCP Server: http://localhost:3001/mcp
• Open WebUI: http://localhost:3002

Security Notes (Important)

• This stack is for local development/testing.
• OpenSearch security plugins are disabled in docker-compose.yml.
• Do not expose these ports directly to the public internet.
• Never commit a real .env file with secrets.

1. Setup

copy .env.example .env

Edit .env and set:

• WEBUI_SECRET_KEY to a long random value (required)
• OPENAI_API_KEY (optional)

2. Start All Services

docker compose up -d --build

Check status:

docker compose ps

3. Configure MCP Tool Server in Open WebUI

1. Open http://localhost:3002 and sign in as admin.
2. Go to Admin Panel -> Settings -> Tools (or Tool Servers, depending on Open WebUI version).
3. Add a new tool server with:
   • Type: MCP
   • Name: OpenSearch MCP
   • ID: opensearch_mcp
   • URL: http://opensearch-mcp:3001/mcp
   • Auth: None
4. Save the server and run connection check/sync if the button is available.
5. Confirm tools are visible (for example cluster_health, list_indices, search_indices).

If your environment cannot resolve Docker service names from Open WebUI, use:

• http://host.docker.internal:3001/mcp

4. Attach MCP Tools to One Model (Example: GPT-4o mini)

1. In Open WebUI, ensure your OpenAI provider is configured with your API key.
2. Open Models and select gpt-4o-mini (or create a custom model entry mapped to gpt-4o-mini).
3. Enable model capabilities for tools/function calling.
4. In the model tool settings, allow/select only the opensearch_mcp tool server.
5. Save the model configuration.
6. Start a new chat and pick gpt-4o-mini.
7. In chat tool controls, ensure tools are enabled and opensearch_mcp is active.

Note: exact menu labels differ slightly by Open WebUI version, but the flow is always: Tool Server setup -> Model tool enablement -> Enable tools in chat.

5. Verify

Use the configured model (gpt-4o-mini) and send:

Use MCP tools only.
Call cluster_health and return cluster_name, status, number_of_nodes, active_primary_shards.
Do not answer from memory.

Expected behavior:

• The assistant performs a tool call to cluster_health.
• The response includes live cluster fields from OpenSearch.

6. Stop

docker compose down

To remove volumes too:

docker compose down -v