8.2 — MCP Server Development

CCDV-F Domain 8 · Task 8.2

What You Need to Know

MCP is a standard protocol for connecting an application to an outside system. An MCP server wraps the system and offers capabilities. Tools a server offers are ordinary tools — everything in 8.1 applies.

Host, Client, Server

• MCP Host — the AI application that coordinates one or multiple MCP clients
• MCP Client — maintains a connection to an MCP server and obtains context for the host
• MCP Server — provides context to MCP clients

The host creates one client per server. Local and remote describe where a server runs, not what it is.

Three Primitives, Three Controllers

Primitive	Who decides	What it is
Tools	Model	Functions the LLM actively calls
Resources	Application	Passive read-only data sources (URI or template)
Prompts	User	Pre-built instruction templates; explicit invocation (slash commands)

The usual mistake is to make all three into tools. Passive reference data → resource. Standard document template a person pulls in → prompt.

Transport Follows Topology

• Stdio — local processes on the same machine; optimal performance; typically single client. Server must not write non-MCP messages to stdout (log to stderr).
• Streamable HTTP — remote communication; supports standard HTTP auth; typically multi-user.

Selection rule: who needs to reach this server, and from where? A remote server is a service — version, owner, availability, authentication, access control.

Reaching a Server from a Claude Application

MCP connector on the Messages API: connect to remote MCP servers without a separate client. Limitations: (1) only tool calls supported; (2) server must be publicly exposed through HTTP. Local stdio servers and prompts/resources need a client-side connection via SDK helpers.