Stacks and Flows

What Changed · Source-verified

MCP 2026-07-28: what changed for builders

The July specification update changes the protocol surface that MCP implementers must track. Treat the versioned specification and roadmap as the boundary; do not infer universal client or server support.

Verified change record

  • The MCP project published a dated 2026-07-28 specification update.
  • SEP-2640, the Skills extension, is Accepted on the extensions track, while the ext-skills Working Group repository remains an experimental incubation space.
  • Accepted specification status does not prove Inspector, SDK, client, server, or ecosystem-wide implementation coverage.
  • The official roadmap identifies current priorities separately from shipped specification requirements.

Specification status is not implementation status

SEP-2640 is Accepted; calling the specification itself only experimental is stale. The ext-skills repository still labels its Working Group material experimental, and tooling support continues to develop. State both facts instead of collapsing them.

Implementation is not ecosystem maturity

A client or server can implement skills/list and skills/get without proving broad interoperability. Record the extension identifier, tested implementations, digest behavior, resource limits, and fallback path before relying on it.

The durable record to keep

Record the specification date, accepted extensions, negotiated capabilities, and tested client-server pairs. Those facts remain useful after the announcement cycle ends.

Decision detail

  1. Pin the protocol and extension versions your integration actually supports.
  2. For Skills over MCP, record three separate facts: specification status, named implementation support, and ecosystem maturity.
  3. Test interoperability against named clients and servers rather than the abstract protocol alone.
  4. Keep incubating repository work out of production requirements unless the selected implementation supports it.

Evidence

These claims are source-verified. We do not label this page hands-on or benchmarked because no reproducible test artifact is attached.

Continue the decision