How to Build an MCP Server: Architecture, Frameworks, Code Structure, and Best Practices

MCP Is the New Standard for AI Integration. But Most Teams Don’t Know How to Build It Properly

Model Context Protocol (MCP) is transforming how SaaS products integrate with AI. It gives language models structured, validated, permission-controlled access to tools, data, and internal services safely.

But here’s the truth:

Building a production-ready MCP server is not the same as building a simple requires architecture design, schema planning, tool strategy, safe execution, validation layers, and an understanding of LLM behavior.

This article provides a hands-on, engineering-level guide for CTOs, architects, and senior developers who want to build an MCP server from scratch. We’ll cover:

• How MCP works internally

• Architectural layers & patterns

• Schema design & validation

• Tool structure & execution

• Error handling

• Messaging strategies

• Infrastructure & deployment

• Real code examples

• What to avoid

And importantly:

Invatechs has built production-ready MCP servers for SaaS companies and AI-driven startups. If you want a reliable implementation, we’ve got you covered.

Let’s dive in.

How MCP Works at a Low Level

Before building anything, engineers must understand MCP’s core design principles:

1. Tools

Functions exposed to the LLM with strict input/output schemas.

2. Resources

Long-lived objects (documents, data structures, knowledge sources) the LLM can access.

3. Prompts

Context templates the AI can reference.

4. Bidirectional communication

The LLM can request tool execution; your MCP server returns structured responses.

5. Safety model

MCP enforces controlled capabilities. No random actions.

MCP Server Architecture (Invatechs Standard Blueprint)

A professional MCP server requires 6 layers:

Layer 1 — API & Transport Layer

Handles:

• Streaming

• Request routing

• Message formatting

• Authentication

Most servers use:

• Node.js

• Python

• Go

Invatechs recommends TypeScript for predictable schemas.

Layer 2 — Schema Definition Layer

This is where developers define:

• tool input schema

• output schema

• error schema

Using Zod or JSON Schema.

Example (TypeScript + Zod):

import { z } from "zod";

export const CreateTicketInput = z.object({
  customerId: z.string(),
  description: z.string(),
  priority: z.enum(["low", "medium", "high"])
});

export const CreateTicketOutput = z.object({
  ticketId: z.string(),
  status: z.string(),
});

Schemas prevent LLM hallucinations by validating requests.

Layer 3 — Tool Execution Engine

Each tool must have:

• pure business logic

• external dependency injection

• safe execution

• timeouts

• error boundaries

Tool Example:

export const createTicket = async (input, context) => {
  const { customerId, description, priority } = input;

  const ticket = await context.crm.createTicket({
    customerId,
    description,
    priority,
  });

  return {
    ticketId: ticket.id,
    status: "created"
  };
};

Invatechs Tip:

Always separate “business logic” from “MCP tool wrapper” to prevent coupling.

Layer 4 — Business Logic Layer

This includes:

• core services

• domain logic

• rulesets

• DB queries

• microservice orchestration

Invatechs uses clean architecture, enforcing clear boundaries:

/domain
/usecases
/integrations
/mcp-tools

Layer 5 — Integration Layer

Connects your MCP server to:

• databases

• CRMs

• billing systems

• internal APIs

• cloud services

Design patterns used:

• Repository

• Gateway

• Adapter pattern

Layer 6 — Security & Observability Layer

Includes:

• audit logs

• request validation

• access control

• rate limiting

• error logs

• tracing

• monitoring

Invatechs strongly recommends implementing multi-level guardrails.

MCP Tool Design Patterns

When building MCP tools, use predictable patterns.

Pattern 1 — Simple Action Tools

Great for CRUD:

• createRecord

• updateCustomer

• triggerEmail

Pattern 2 — Workflow Tools (Invatechs Recommended)

Combines multiple actions:

export const onboardCustomer = async (input, ctx) => {
  const profile = await ctx.db.createProfile(input);
  await ctx.email.sendWelcome(profile.email);
  await ctx.crm.createRecord(profile);
  return { message: "Onboarding complete" };
};

Pattern 3 — Data Retrieval Tools

Good for analytics:

export const getRevenueReport = async (input, ctx) => {
  return await ctx.analytics.generateRevenue(input.period);
};

Pattern 4 — Orchestration Tools

These are powerful: LLM triggers a sequence of events.

Pattern 5 — Validation-first Tools

Always validate early.

MCP Server Example (Minimal Implementation)

Below is a simplified MCP server structure using TypeScript.

import { Server } from "mcp-framework";
import { createTicket } from "./tools/createTicket";
import { CreateTicketInput, CreateTicketOutput } from "./schemas";

const server = new Server({
  tools: [
    {
      name: "create_ticket",
      inputSchema: CreateTicketInput,
      outputSchema: CreateTicketOutput,
      execute: createTicket
    }
  ],
  context: {
    crm: new CRMClient(),
    email: new EmailService()
  }
});

server.start(3000);

A production version requires:

• error middleware

• auth layer

• context augmentation

• structured logs

• request tracing

• environment configs

Invatechs implements all of this.

Error Handling & Safety

LLMs make mistakes. Your server must detect and correct them.

Add error envelopes:

throw new MCPError("INVALID_INPUT", "Customer not found");

Validate output as well

Yes — validate both directions.

Log every tool call

Audit logs are mandatory.

Connecting MCP to LLM Agents

There are three typical ways:

1. Direct LLM Integration (OpenAI / Anthropic)

Useful for SaaS applications.

2. AI Agent Frameworks

Examples:

• LangChain

• CrewAI

• Autogen

• Semantic Kernel

3. Custom Agent Layer (Invatechs Recommended)

Gives full control.

Deployment Strategies (The Invatechs Way)

MCP servers run best with:

1. Docker containers

Predictable environments.

2. Kubernetes or ECS

Scalable orchestration.

3. Load balancers (Nginx / ALB)

Handles agent concurrency.

4. Monitoring stack

• Grafana

• Prometheus

• DataDog

5. Automated CI/CD

GitHub actions + IaC (Terraform).

6. Secrets management

Vault or AWS Secrets Manager.

Invatechs provides a full production set-up.

Real-world Example Architecture

Imagine a SaaS CRM wants MCP access. Architecture:

AI Agent
   ↓
MCP Server
   ↓
Business Logic Layer
   ↓
CRM Database / Stripe / Email / Admin panel

The LLM can now:

• create contacts

• generate reports

• run onboarding

• update subscriptions

• produce insights

Should Your SaaS Company Build an MCP Server? Checklist

If you answer “yes” to 3 or more — MCP is a perfect fit:

• Do you have repetitive workflows?

• Do employees handle tasks manually?

• Do customers expect AI features?

• Do you want to automate CRM/Billing/Admin actions?

• Do you want AI agents to perform real work?

• Do you have multiple internal systems?

• Do you want to improve engineering velocity?

If so:

Invatechs can architect, build, integrate, secure, and deploy your MCP server end to end.

Building MCP Servers Requires Real Engineering Expertise

MCP is not a plug-and-play feature. It’s a deep architectural component that requires:

• backend engineering

• AI agent experience

• schema design

• security modeling

• validation rules

• workflow orchestration

• integration engineering

• DevOps deployment

Most teams underestimate the complexity.

Invatechs helps SaaS companies and startups build MCP servers that are:

• production-ready

• secure

• scalable

• cleanly architected

• deeply integrated with your business tools

• optimised for real AI agents

If you need an MCP partner, we’ve got you covered.