Model Context Protocol (MCP) — Complete Guide for Backend Engineers
Build Tools, Resources, and AI-Driven Services Using LangChain
Modern LLM-based applications are no longer just about generating text — they need to interact with real systems:
✅ Databases
✅ File systems
✅ Internal microservices
✅ Web APIs
✅ Analytics engines
✅ Cloud services
To support this, OpenAI introduced MCP — Model Context Protocol, a powerful standard that lets LLMs communicate with tools using a safe, structured API.
This guide gives you:
✅ Clear concepts
✅ Interview-focused explanations
✅ Step-by-step MCP server creation
✅ Examples using LangChain
✅ Text-based architecture diagrams
Perfect for your blog.
What Is MCP?
MCP (Model Context Protocol) is a unified protocol that allows AI models to access tools, resources, and files in a structured manner.
Think of it as an API gateway for LLMs.
Instead of relying only on prompts, LLMs can call tools like:
MCP provides:
✅ A standard interface
✅ Strong typing
✅ Clear request/response format
✅ Security boundaries
✅ Cross-language interoperability
๐ High-Level Architecture (Text-Based Diagram)
๐ MCP Transport Protocols
MCP defines how an AI agent connects to your server:
✅ 1. stdio (local execution)
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Uses stdin/stdout for message passing
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Zero network overhead
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Ideal for CLI tools, dev workflows
✅ 2. websocket (remote execution)
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Perfect for cloud microservices
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Works with Kubernetes, ECS, GKE, etc.
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Supports multiple LLM clients
✅ 3. HTTP (proxy adapters)
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HTTP isn't native in MCP but supported via
Nginx/Envoy/Gateway adapters.
๐ ️ Building a Simple MCP Server (LangChain)
Below is a minimal MCP server using LangChain + FastAPI.
✅ Install dependencies
✅ Step 1: Create Tools
✅ Step 2: Create the MCP Server
✅ Step 3: Run the MCP Server
MCP endpoint available at:
๐งฐ Exposing Resources
You can expose static or dynamic resources:
๐ Exposing File-System Resources (Read-Only)
๐ค How Agents Call MCP Tools (LangChain)
๐ฏ Tool Invocation Flow
Detailed:
๐ผ Where Backend Engineers Use MCP
✅ Integrating LLMs with microservices
✅ Allowing safe access to production data
✅ Creating API-driven agents
✅ Building internal developer tooling
✅ Simplifying multi-agent systems
✅ Enabling plug-and-play AI behavior
๐ค Interview-Ready Explanation
Q: What problem does MCP solve?
✅ Standardizes how AI models interact with external tools
✅ Makes tool usage safe, typed, predictable
✅ Enables multi-tool, multi-resource workflows
Q: How does an agent know which tool to call?
The LLM sees tool schemas + natural language description →
Uses reasoning + training → selects correct tool.
Q: What’s the difference between stdio and websocket?
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stdio: Local execution
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websocket: Cloud execution
Q: What can MCP expose?
✅ tools
✅ resources
✅ file systems
๐ฆ Full Project Structure
๐ Summary Table
| Feature | Description |
|---|---|
| Tools | Functions agent can execute |
| Resources | Static/dynamic information exposed to LLM |
| FileSystem | Safe, restricted directory access |
| Protocols | stdio, WebSocket, HTTP (proxy) |
| Language Support | Python, JS, Java (soon), Go (soon) |
| Architecture Style | JSON-RPC 2.0 |
✅ Final Thoughts
MCP is quickly becoming the standard protocol for LLM-to-system integration.
For backend engineers, knowing MCP gives you a huge advantage in:
✅ AI system design
✅ Multi-agent architectures
✅ Tooling integration
✅ LLM-powered microservices