Are you looking up what the abbreviation stands for, or what an MCP is?

The first case doesn't matter at all if you already know what an MCP actually is.

At least for the task of understanding the article.

MCP being the initialism for "Model Context Protocol", the specification released by Anthropic, generally dictates you shouldn't say "an MCP" but simply "MCP" or "the MCP". If you are referring to a concrete implementation of a part of MCP, then you likely meant to say "an MCP Server" or "an MCP Client".