Short call

Use MCP when multiple clients need the same tool surface and the permissions can stay narrow. Use direct API tools when the integration is small, critical, and easier to audit in code.

What to test

• List every write-capable tool exposed to the agent.
• Confirm logs show inputs, outputs, and side effects.
• Check whether a single action can spend money, delete data, or message users.
• Disable the server and verify the system fails closed.

Watch for

Convenient tool access is not automatically good operations. A broad MCP server can turn a simple task into an oversized trust boundary.