Easy MCP Client

Overview

This project delivers an end-to-end conversational assistant that combines a FastAPI backend, a Streamlit chat UI, and a Model Context Protocol (MCP) gateway so the assistant can call external tools (e.g., Tavily search). The API wraps a Docker Model Runner-hosted LLM endpoint behind an OpenAI-compatible interface, persists chat history in memory, and exposes endpoints for health checks, chat, and troubleshooting.

Architecture & Capabilities

• FastAPI service (api/): boots with a lifespan hook that connects to the MCP gateway, discovers remote tools, and registers them on a shared LLM client for tool calling.
• LLM client (api/services/llm_client.py): async wrapper around an OpenAI-style /chat/completions endpoint with tool support, structured output, and conversation tracking.
• Conversation store (api/services/in_memory_store.py): thread-safe in-memory history store used by the LLM client (intended to be swappable).
• Streamlit UI (ui/app.py): provides a simple chat experience against the FastAPI backend.
• Docker Compose (compose.yaml): orchestrates the API, the Streamlit UI, and a docker-based MCP gateway.

Tech Stack

• FastAPI for the HTTP API.
• Streamlit for the web UI.
• fastmcp client library for Model Context Protocol access.
• HTTPX for async HTTP calls with HTTP/2 support.
• Docker / Docker Compose for containerized deployment, including Docker Model Runner integration.
• Python 3.13 (see Dockerfile) with type hints and pydantic settings management.

Prerequisites

• Docker Model Runner with a model pulled from Docker Hub.
• Docker Desktop with the Docker MCP Toolkit extension enabled.
• At least one MCP server added in Docker Desktop (e.g., Tavily) so the gateway can proxy tool calls.
• For servers that require credentials, populate the server's Configuration secrets section (Docker Desktop > Docker MCP Toolkit > your server > Configuration > Secrets) with the necessary key/value pairs so they are mounted for API and gateway containers.

Note: This project was tested with qwen3:0.6B-Q4_K_M. A reasoning model is highly recommended to be used with this project.

Running Locally (without Docker Compose)

1. Ensure Python 3.11+ (tested with 3.13) and install dependencies: pip install -r requirements.txt.
2. Configure environment variables (e.g., DMR_MCP_URL, LLM_MODEL_URL, LLM_MODEL_NAME) via .env:

   DMR_MCP_URL=http://localhost:8080/mcp
   API_BASE_URL=http://localhost:8000
   LLM_MODEL_URL=http://localhost:12434/engines/llama.cpp/v1/
   LLM_MODEL_NAME=
   

3. Important: before starting the API, launch the MCP gateway using the command:

   docker mcp gateway run --port 8080 --transport streaming
   

   Leave this process running; the API will connect on startup.
4. Start the FastAPI server:

   uvicorn api.main:app --host 0.0.0.0 --port 8000
   

5. In a separate terminal, run the Streamlit UI (optional):

   streamlit run ui/app.py
   

   It expects API_BASE_URL (default http://localhost:8000).

Running with Docker Compose

1. Populate .env.docker with the required values (provided defaults target the compose network):

   DMR_MCP_URL=http://mcp_gateway:8080/mcp
   API_BASE_URL=http://api:8000
   

2. From the project root, start the stack:

   docker compose up --build
   

   This launches:
   • mcp_gateway on port 8080
   • api on port 8000 (health check at /healthz)
   • ui on port 8501 for the Streamlit interface
3. Visit http://localhost:8501 to interact with the assistant.

Docker Compose automatically injects the model endpoint and name into the API container when you use the long syntax models block:

models:
  llm:
    endpoint_var: LLM_MODEL_URL
    model_var: LLM_MODEL_NAME

See the Docker documentation for details: https://docs.docker.com/ai/compose/models-and-compose/

Using the LLM Client

The LLMClient abstraction (in api/services/llm_client.py) wraps an OpenAI-compatible chat endpoint while managing conversation history and tool execution. Typical workflow:

1. Instantiate the client with a base URL, model name, a ConversationStore implementation, and optional system instructions.
2. Register tools with register_tool, providing a callable (sync or async) and a JSON schema describing its parameters.
3. Generate responses via await generate(...); the client sends accumulated history, invokes tools as needed, and can enforce structured responses when you pass response_schema.
4. Close the client with await close() when finished so the underlying HTTPX session is released.

Example usage in an async context:

from api.services.in_memory_store import InMemoryStore
from api.services.llm_client import LLMClient

store = InMemoryStore()
client = LLMClient(
    base_url='http://localhost:1234/',
    model_name='ai/granite-4.0-h-micro',
    store=store,
    instructions='You are a helpful assistant.',
)

def echo_tool(message: str) -> str:
    return message

client.register_tool(
    func=echo_tool,
    description='Echo the provided message.',
    parameters_schema={
        'type': 'object',
        'properties': {'message': {'type': 'string'}},
        'required': ['message'],
    },
)

response = await client.generate('Hello there!', thread_id='demo-thread')
print(response)

await client.close()

Roadmap

• Persistent conversation store: replace the in-memory store with Redis (or equivalent) to support multi-instance scaling and durable histories.
• Thread isolation: implement proper thread identifiers per user/session to prevent shared histories and enable concurrent conversations.
• Enhanced UI: iterate on the Streamlit front-end (or migrate to a richer framework) for features like conversation lists, tool call inspection, and error feedback.
• Observability: add logging, metrics, and tracing around LLM/tool calls for debugging and monitoring.
• Secrets management: integrate secure secret storage for API keys instead of relying on plain .env files.

Contributing

Issues and pull requests are welcome. Please run formatting and linting checks before submitting changes and ensure new features include adequate tests.