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.

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.