3.7 — Choosing the Integration Mechanism

CCAR-P Domain 3 · Task 3.7

What You Need to Know

Four mechanisms connect Claude to surrounding systems:

Mechanism	Selection cue	Wrong when
MCP server	Capability reused across surfaces/teams/clients	One consumer, no sharing ambition
Direct API/SDK	One application, full control, custom loop	A second surface or team appears
Headless (SDK/CLI)	Pipelines, CI, cron — script consumes parsed output	Human interactive surface is the consumer
Agent-to-agent	Counterpart reasons and decides for itself	Counterpart executes a fixed operation

MCP Collapses M×N to M+N

Build a server once; any MCP client uses it. Transports: stdio (local subprocess) and streamable HTTP (remote, shared, multi-client). Streamable HTTP is still MCP — transport is deployment topology, not protocol choice.

Agent-to-Agent Test

Does the counterpart reason? Yes → agent. No (fixed, fully-specified operation) → plain tool call.

Key Concept: Count the consumers and surfaces. The impressive mechanism planted where the boring one is right is the signature distractor.

Exam Traps

• Standing up an MCP server for a bespoke single-consumer integration
• Ruling MCP out because deployment needs HTTP (or treating stdio as the only real MCP)
• Delegating to a peer agent whose task is a deterministic fixed operation
• Adding interactive machinery (streaming/chat) to a nightly pipeline job