MCP by default

As the Model Context Protocol (MCP) gains traction, we're seeing teams and vendors reach for it as the default integration layer between AI agents and external systems, even when simpler alternatives exist. We caution against using MCP by default. MCP adds real value for structured tool contracts, OAuth-based authentication boundaries and governed multi-tenant access. It also introduces what Justin Poehnelt calls an "abstraction tax": every protocol layer between an agent and an API loses fidelity, and for complex APIs those losses compound.

In practice, a well-designed CLI with good --help output, structured JSON responses and predictable error handling often gives agents everything they need without the protocol overhead. As Simon Willison notes, "almost everything I might achieve with an MCP can be handled by a CLI tool instead."

This isn't a rejection of MCP. Teams should avoid adopting it by default and first ask whether their system actually requires protocol-level interoperability. MCP makes sense when its governance and integration benefits outweigh the added complexity and potential fidelity loss.