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Clear ideas, no jargon, so you can follow what all of this is about.

Before reading the more technical pages in this section, it helps to be sure about the words. No formulas and no jargon: explanations you get on the first pass.

What an API is

API stands for Application Programming Interface. It sounds technical, but the idea is simple:

An API is how two programs talk to each other, with no humans in between.

The restaurant analogy explains it well:

  • You (an app) sit down at the table.
  • The waiter is the API.
  • The kitchen is the other system (a bank's database, say, or Gmail's server).

You do not walk into the kitchen or shout at the chef. You order from the waiter (the API) off a menu with specific options: "bring me dish 5". And that is exactly what arrives. The menu is the contract: it defines what you can ask for and what you get back. No more, no less.

Examples you use without noticing:

  • When a website lets you "pay with PayPal", that site is talking to PayPal through its API.
  • When you check the weather on your phone, the app asks a weather company's API for the data.
  • When Vaucai reads your Gmail, it talks to Google's API.

What a "REST API" is

REST is simply the most common style of building an API today. It is not a different thing: it is an API that follows a few specific conventions:

  • It talks over the internet (HTTP), the same technology your browser uses.
  • Every thing has an address (a URL), for example .../invoices/123.
  • And you use a set of standard verbs:
GET
give me / read (fetch an invoice)
POST
create (make a new invoice)
PUT / PATCH
modify
DELETE
delete

When someone says "connect over the REST API", they mean: "talk to my system over the internet, asking for things with those URLs and those verbs". Most modern services (Holded, Factorial, a CRM and so on) offer a REST API.

A useful detail. Many REST APIs come with a "printed menu" called OpenAPI (formerly Swagger). It is a file that describes, in a way a machine understands, every available operation and what data each one takes. It is literally the restaurant menu in a standard format. This matters for the Vaucai part, as you will see.

What MCP is

MCP stands for Model Context Protocol. It is much newer than APIs: Anthropic, the company behind Claude, published it in late 2024. It was born for one specific problem:

How to connect an AI (like your Vaucai) to outside tools and data, in a standard way.

The most used analogy is USB for artificial intelligence: before, every device had its own cable and a mess of connectors. USB arrived and suddenly everything plugged in the same way. MCP wants to be that: a standard socket. So any AI can connect to any tool without programming a bespoke integration for each one.

The key difference from a normal API:

  • A REST API is designed for programmers to use. The "menu" is written for humans who code.
  • An MCP server is designed for an AI to use directly. It exposes its tools in a way the model understands on its own: "I have these 3 actions, they are called this, and they are for that". Your Vaucai reads that list and decides when to use them itself, mid conversation.

A concrete example: there is an MCP server for GitHub. Connect it to your Vaucai and your Vaucai can "open issues" or "read code" on its own when the conversation calls for it, because the MCP server offers those tools already prepared for an AI.

Underneath, an MCP server often ends up calling a normal REST API anyway. The point of MCP is its translation layer: it makes the AI understand it without programming each integration.

The distinction that ties it all together: two directions

This is the most important thing to take away, because it is the key to understanding what Vaucai does. With both APIs and MCP there are two directions:

Outbound

Your Vaucai consumes. It uses outside tools (your CRM, your MCP server) to do things for you. This is your Vaucai going out to use your tools.

Inbound

Your Vaucai is exposed. Other apps talk to your Vaucai and ask it for things. It is like giving it a doorbell so others can call.

Almost all the confusion about "MCP and APIs" comes from mixing up these two directions. In Vaucai you will see that we offer some things one way and some the other, and not all of them. The next two pages in this section are, precisely, one for each direction.

Looking for something specific? Browse the full catalogue of what your Vaucai can do. And if you don't have yours yet, create it now: three steps and about a minute.