What integration problem does MCP solve?

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Quick reference

TL;DR

MCP turns the M×N integration explosion into M+N: each host speaks MCP once, each tool exposes MCP once, so they all interoperate without bespoke pairwise glue.

Memory aid

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Easy to grasp

Picture a world before standard wall sockets, where every appliance needed its own custom plug for every house. A toaster wired for one home would not fit the next. If you had many homes and many appliances, you wired a unique connection for every single pair, an explosion of one-off adapters. Then everyone agreed on one socket shape. Now each home installs that socket once, and each appliance ships one matching plug once. Any appliance works in any home. MCP is that shared socket for AI apps and tools. Each app learns to speak MCP a single time, each tool exposes MCP a single time, and suddenly every app can use every tool. No more hand-wiring a custom connector for each app and tool combination.

Key concepts

M×N integration problem AI agents LLM tool use

Quick scan · 2–4 min

Everything important, quickly.

3 min: state the M×N product, derive the M+N collapse, give the USB-C analogy, then name the decoupling win and when to skip MCP.

Side-by-side

Concern	No shared standard	With MCP
Integration count	M × N bespoke adapters	M + N (one per side)
Adding a new tool	Update every existing host	Ship one MCP server
Adding a new host	Re-integrate every tool	Implement one MCP client
Scaling behavior	Multiplicative, super-linear in practice	Linear in hosts plus tools
Tool reuse across apps	None; each pairing is custom	Write once, runs in any host

Real-world examples

Real products, models, and research that use this idea.

Anthropic released MCP in November 2024 with official servers for filesystem, Postgres, Git, GitHub, and Slack as drop-in plug-ins.
Cursor and Zed adopted MCP in 2025, so a server written for Claude Desktop runs unchanged in either editor.
The mcp.so marketplace lists hundreds of community servers, each written once and usable by any MCP-aware host.

Interviewer follow-ups

What an interviewer would ask next. Try answering before peeking at the approach.

QWhy is the pre-standard cost often worse than a clean M×N would suggest?

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QHow is the M+N argument similar to a narrow-waist design in networking or compilers?

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QWhen is the M×N problem too small to justify adopting MCP?

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60-second cheat sheet

The night-before-the-interview bullets. Scan these on the way to the call.

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References

Primary sources. Skim if you want the original framing.