Show HN: Only 1 of 4,356 reachable MCP servers is ready for the 2026-07-28 spec

Overview

Is your remote MCP server ready for the 2026-07-28 MCP spec release? Find out in 30 seconds.

npx mcp-spec-check https://your-server.com/mcp

Nothing breaks on July 28. That date is when the spec text publishes, not a switch that flips. Version negotiation keeps working and deprecated features live for at least 12 months. This tool measures adoption of the new stateless core, not a countdown to an outage.

The MCP 2026-07-28 release is the largest revision of the protocol since launch. The initialize handshake and Mcp-Session-Id are removed in favor of a stateless core, Mcp-Method / Mcp-Name routing headers become required, SSE elicitation is replaced by Multi Round-Trip Requests, and several error codes change. SDKs and clients are already moving to the stateless core, so servers that never migrate get left behind as support windows expire.

mcp-spec-check black-box-probes your live endpoint (no code access needed) and tells you where you stand, with links to the migration docs.

Registry Scan Results

I probed every remote server in the official MCP registry, all 7,850 of them, on 2026-07-12. Of the 4,356 I could reach openly, exactly 1 passes all three required checks and 90.8% are not ready yet. The migration to the stateless core has barely begun, which is what you would expect before the spec is even GA.

Full writeup, with every percentage next to its denominator and a host-collapsed sensitivity view: docs/scan-2026-07.md (committed aggregate: scan-2026-07.aggregates.json).

Report Format

The report leads with a one-line verdict, ready for 2026-07-28: YES / NO / UNKNOWN, decided only by the three required checks below (discover, routing-headers, session-independence): all three pass gives YES, any fail gives NO, otherwise UNKNOWN. A letter grade over every check follows as a secondary signal. Only those first three can fail a server. The rest are warn: optional or forward-looking, never counted as "not ready" on their own. A check the server answers too ambiguously to judge is marked inconclusive and, like a skipped check, does not count toward the grade. If too many land there, the tool reports grade ? ("couldn't assess", exit 2) rather than guess.

Required and Optional Checks

Probe Correctness

Probe correctness is the whole game, so every check is pinned against known-truth servers rather than just asserted:

• Two reference servers run in CI. A real old-spec server (official SDK v1) and an RC server (the 2026-07-28 SDK beta) are spawned on every build, and mcp-spec-check must produce the exact expected verdict for all eight checks against both (npm run verify:refs). A regression in either direction fails the build.
• A known-truth panel cross-checks live public servers whose behavior is established, including GitHub's MCP server (auth-walled, RFC 9728 passes) and servers that should read as not-ready or inconclusive.
• The official conformance suite runs against the RC reference server as an independent co-oracle.

If the tool ever gives your server a wrong verdict, that is the top-priority bug. Open an issue with the --json output.

Usage

npx mcp-spec-check                          # human-readable report + letter grade
npx mcp-spec-check --json                   # machine-readable, for scripting
npx mcp-spec-check --verbose                # include the "why" for each check
npx mcp-spec-check --timeout 30000          # per-probe timeout in ms (default 15000)
npx mcp-spec-check --bearer                 # sends Authorization: Bearer
npx mcp-spec-check --header "X-Api-Key: k"  # any header; repeatable

Without credentials, mcp-spec-check can classify an auth-walled server but cannot grade it: checks report skipped and the exit code is 2 (couldn't test). The auth-metadata check still runs, because its RFC 9728 probe of /.well-known/oauth-protected-resource is origin-level and needs no token, so you get a readiness signal even behind the wall.

Exit Codes

Exit codes are CI-friendly:

• 0 ready
• 1 at least one failing check
• 2 couldn't test (probe error; endpoint auth-walled / unreachable / not MCP; or the server answered our probes too ambiguously to grade)

- run: npx mcp-spec-check ${{ env.MCP_SERVER_URL }}

Pure black-box HTTP probes against your live endpoint. No code access, nothing installed, nothing stored. Zero runtime dependencies.

Probing Ethics

The registry scan only touches endpoints voluntarily published in the official public MCP registry as connect URLs. Probes are host-serial (one request at a time per host, so no server ever sees parallel load), read-only protocol calls with no side effects, sent with a named mcp-spec-check-scan User-Agent that links back to this repo. Per-server results stay on the machine that ran the scan; only aggregate counts and percentages are published.

Related Tools

The official conformance suite is a spec test framework for implementers, including draft-spec scenarios, that you wire up against your own code. YawLabs/mcp-compliance grades A to F compliance against the current 2025-11-25 spec. The official Inspector is for interactive debugging. mcp-spec-check is none of those: it is a 30-second black-box verdict on a hosted URL, aimed specifically at the next release (2026-07-28).

Issues and PRs welcome, see CONTRIBUTING.md. Probe correctness is the top priority: if a verdict looks wrong, please include the --json output. MIT.