Short answer. An MCP server is a bridge between an AI assistant (Claude, Cursor, Zed) and external tools or data. It implements the Model Context Protocol — an open standard that lets a model call functions, read resources, and get results in real time. Instead of hallucinating an answer, the assistant queries the server, runs a real check, and returns trustworthy data.
The problem MCP solves
A large language model is isolated on its own: it only knows what was in its training data and cannot perform a single action in the outside world. Ask Claude "what SSL certificate does example.com use," and without tools it will either refuse or invent an answer. The Model Context Protocol, introduced by Anthropic in late 2024, standardizes how an assistant connects to data sources and executable functions.
MCP is often called "USB-C for AI tools": one protocol instead of a dozen incompatible integrations, one per assistant.
Before MCP, every "model ↔ tool" pairing needed its own custom code. Now any MCP-compatible client works with any MCP server — decoupling tool development from assistant development.
How MCP works: three key concepts
- Tools — functions the model can call: "check SSL," "run a DNS query," "scan security headers." Each tool is described by an input schema.
- Resources — data the server returns on request: files, database records, documents.
- Prompts — prepared templates the server offers the client for common scenarios.
Transport varies: local over stdio (the server runs as a process on your machine) and remote over streamable HTTP (the server lives in the cloud, reachable by URL). The second option is more convenient — nothing to install locally.
Minimal client setup
To connect a remote MCP server to Claude Desktop or Cursor, just add its URL to the config. For example, the enterno.io diagnostic server connects like this:
{
"mcpServers": {
"enterno": {
"url": "https://enterno.io/mcp"
}
}
}This block goes into claude_desktop_config.json (Claude Desktop) or your project's mcp.json (Cursor). After restarting the client, the server's tools become available to the assistant.
What changes in practice
Once connected, you write a normal natural-language request, and the assistant decides which tool to call:
Check the SSL chain and DNS records for example.com,
and tell me if there are any security header issues.This prompt makes the assistant call the SSL tool, the DNS tool, and the header scanner in sequence, then merge the results into one analysis — no copy-pasting between separate utilities.
MCP server vs. REST API
It may look like MCP duplicates an ordinary REST API документацию. The difference is the audience and the description format.
| Criterion | REST API | MCP server |
|---|---|---|
| Audience | Code (a developer writes the integration) | AI assistant (it calls on its own) |
| Description | OpenAPI / docs | Self-describing tool schema |
| Auth | API key required | Often optional for public checks |
| Call style | Manual HTTP request | Natural language → auto-call |
Rule: use a REST API when you write the code yourself; use an MCP server when you want an AI agent to act for you, picking tools on the fly.
Example: the enterno.io diagnostic MCP server
enterno.io exposes an MCP server at https://enterno.io/mcp (streamable HTTP) that surfaces 16 site-diagnostic tools: HTTP header checks, DNS, SSL/TLS, Ping, IP geolocation, WHOIS, SEO audit, a security scanner, and an AI-readiness score. No key is needed for public checks — the server is free. There's also an @enterno/mcp-client SDK on npm for programmatic access.
This turns Claude or Cursor into a full network-diagnostics console: you never leave the chat, and the assistant runs the real checks. For more on giving assistants tools, see our piece on API security best practices.
FAQ
Is MCP only for Claude?
No. MCP is an open standard. It's supported by Claude Desktop, Cursor, Zed, and a growing list of other clients. One server works with all of them at once.
Do I need to install anything locally?
For a remote server over streamable HTTP — no. Just add the URL to your client config. Local stdio servers run as a process on your machine.
Is it safe to give an AI access to tools?
Tools only do what their schema describes. The enterno.io diagnostic tools make outbound checks against third-party sites and have no access to your data. Always review which actions a server exposes before connecting.
How is MCP different from plugins?
Plugins are usually tied to one platform. MCP is a cross-platform protocol: the same server serves any compatible client with no rewriting.
Can I check whether my site is ready for AI agents?
Yes — there's a dedicated AI-readiness check that analyzes how accessible your content is to crawlers and assistants.