---
title: "2. Terminology"
description: "MCP Description specification v0.7.0 — 2. Terminology."
source: "https://mcpdesc.org/docs/specification/0.7.0/terminology/"
---

Mirrored specification

This page mirrors **2\. Terminology** of the MCP Description specification **v0.7.0**. The canonical source of truth is [cisco-open/mcptoolkit-contract](https://github.com/cisco-open/mcptoolkit-contract/blob/main/spec/sections/02-terminology.md). Where this page differs from upstream, upstream wins.

## 2\. Terminology

### 2.1 Key Words

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC 2119](https://www.rfc-editor.org/rfc/rfc2119).

### 2.2 Definitions

**MCP Description Document**A JSON document conforming to this specification that describes the capabilities of an MCP server.

**MCP Server**A server implementing the Model Context Protocol, exposing tools, resources, and/or prompts to MCP clients.

**MCP Client**An application that connects to an MCP server using the MCP protocol.

**Tool**A server-side function that an MCP client can invoke with structured input parameters and receive structured output.

**Resource**A server-side data source identified by a URI that an MCP client can read.

**Resource Template**A parameterized resource definition using a URI template (RFC 6570) that can produce resource URIs when template variables are provided.

**Prompt**A server-side prompt template that an MCP client can invoke with arguments to generate messages.

**Transport**The communication mechanism used to connect to an MCP server (e.g., stdio, streamable-http, SSE).

**Specification Extension**A property in an MCP Description document whose name begins with `x-` that provides vendor-specific metadata outside the core specification.

**Capability**A feature or behavior supported by an MCP server, declared in the `capabilities` object.