What are MCP Servers?

Source: fly.io Date: 2025-06-17 URL: https://fly.io/blog/mcps-everywhere/

Summary

Conceptual essay explaining MCP (Model Context Protocol) for a developer audience, framing it as a standardized protocol layer between AI models and external tools — “USB-C for AI integrations.” The key reframe: MCP isn’t about adding AI to existing tools, but adding existing tools to an LLM, which could obsolete traditional app stores. Technical clarifications include that MCP servers maintain long-lived lifecycles (not ephemeral like serverless functions) and have built-in capability discovery via the protocol.

Implications

MCP integration thread. This is a 101-level explainer published on fly.io’s blog, which tells you who fly.io is recruiting as a platform audience: developers who haven’t adopted MCP yet but whose workflows fly.io wants to host. The “adds tools to LLMs” framing versus “adds LLMs to tools” is the sharpest way to capture MCP’s inversion of the typical integration direction. The long-lived lifecycle point matters operationally: MCP servers aren’t request-response, they’re persistent processes — which is exactly what Fly Machines (and especially Sprites) are optimized for. The essay is also a soft recruitment document for the fly mcp launch product announced in the same window.