---
url: /mcp.zig/guide/client-concepts.md
description: >-
  Core MCP client concepts: connecting to servers, discovery, and invoking
  tools, resources, and prompts.
---

# Understanding MCP Clients

MCP clients are instantiated by host applications to communicate with MCP servers. Each client handles one direct communication with one server.

## Core Client Features

In addition to using context from servers, clients provide features *to* servers to enable richer interactions.

| Feature         | Explanation                                                              | Example                                          |
| :-------------- | :----------------------------------------------------------------------- | :----------------------------------------------- |
| **Elicitation** | Enables servers to request information from users during interactions.   | Asking for a missing booking detail.             |
| **Roots**       | Allows clients to specify filesystem boundaries/directories of interest. | "Travel Planning Workspace" folder.              |
| **Sampling**    | Allows servers to request LLM completions through the client (Agentic).  | A server asking the LLM to pick the best flight. |

### Elicitation

Elicitation allows servers to pause operations and ask the user for input (e.g., via a UI form).

* **Protocol**: `elicitation/requestInput`
* **Flow**: Server requests -> Client shows UI -> User inputs -> Client returns execution.

### Roots

Roots communicate filesystem access boundaries.

* **Protocol**: `roots/list`
* Roots are advisory boundaries (folders) telling the server where to focus.

### Sampling

Sampling enables servers to perform AI tasks using the Host's LLM connection.

* **Protocol**: `sampling/createMessage`
* **Control**: Puts the client/user in control of permissions, costs, and model selection.
* **Human-in-the-loop**: Users can review sampling requests.