What is an MCP server? Explained simply.
An MCP server is a connection through which ChatGPT or Claude can ask a service instead of guessing. Here with the example of EINI and this week's deals.
MCP stands for Model Context Protocol. It is an open standard that lets AI assistants such as ChatGPT and Claude use the tools and data of other services. The service provides an MCP server; the assistant calls it when a question needs it.
Anthropic published MCP in November 2024; since December 2025 it has been part of the Linux Foundation's Agentic AI Foundation. ChatGPT calls these connections apps or connectors, Claude calls them connectors.
Updated 20 Oct 2026What happens when you ask
- You ask“Which coffee deals are on at Denner this week?”
- The assistant picks a toolClaude or ChatGPT sees that the EINI server offers a tool for deals and calls it with “coffee” and “Denner”.
- The server answers with dataThe EINI server searches this week's deals and sends back products, prices, discounts, validity and source.
- The assistant writesFrom that data, the assistant writes the answer. The figures come from the server, not from the model's memory.
The tools of the EINI server
- Search deals
- This week's deals at Coop, Migros, Lidl, Aldi, Denner, Aligro, Volg and Otto's. No account.
- Compare health insurers
- The official 2027 basic insurance premiums by municipality, age, deductible and accident cover. No account.
- Read meal plan and shopping list
- Your current weekly plan and list. Only with the EINI login.
- Create a new plan
- A weekly plan built from this week's deals. Only with the EINI login.
MCP, web search and APIs compared
| Web search | MCP server | |
|---|---|---|
| Where do the figures come from? | From whatever web pages are found | Straight from the service |
| Up to date? | Depends on the page found | As current as the service's data |
| Structured (price, discount, date)? | Rarely | Yes |
| Personal data? | No | Only after login, if you want it |
An API is a service's technical interface for developers. MCP defines how AI assistants find and use such interfaces: the server describes its tools, and the assistant decides when it needs them.
What is sent and what is not
- Only the request
- The assistant sends the server the parameters, for example “coffee, Denner”. The server does not see the whole chat.
- Only what the server offers
- An MCP server can only run the tools it publishes itself. At EINI, the public tools are read-only.
- Login only for personal data
- For your meal plan, you sign in to EINI through OAuth. Neither ChatGPT nor Claude sees your password.
Only connect servers from services you trust, just as you only install apps you trust.
MCP stands for Model Context Protocol. It is an open standard through which AI assistants use the tools and data of other services. Anthropic published it in November 2024; today it is part of the Linux Foundation's Agentic AI Foundation.
The idea is similar: both extend an assistant. But MCP is an open standard. The same server works with different assistants, for example Claude and ChatGPT.
No. You add the server in the assistant's settings with a URL. With EINI it takes about two minutes.
Yes. ChatGPT supports MCP servers as apps and connectors; your own servers can currently be added in developer mode. Claude supports them as custom connectors.
Yes, for example EINI: it provides the weekly deals of eight Swiss chains and the official 2027 health-insurance premiums. As far as we know (October 2026), EINI is the first Swiss savings app with its own MCP connector.