Most SaaS companies now ship an official remote MCP server, and most of them sit behind OAuth. We wanted to know how closely those servers follow the current MCP authorization spec (the 2026-07-28 revision), so we checked the official servers of 67 vendors from the outside. 61 of them require a login. This post is about those 61.
The short version: the basics are done everywhere. The newer parts of the spec are not.
We used our free MCP Server Check. It is passive. For each server it sends one unauthenticated initialize request, reads the public OAuth discovery documents, and calls tools/list only if the server answers without a token. It never calls a tool and never sends a token.
We ran every server on October 26 and again on November 4, 2026. The numbers below are from November 4. Results are point in time and checked from Cloudflare's network, so a server can look different from another network or a few days later.
All 61 answer an anonymous request with HTTP 401, and all 61 advertise PKCE with S256. That is the part of the spec that stops the most obvious mistakes, and nobody skipped it.
56 of 61 also publish OAuth Protected Resource Metadata (RFC 9728) and point to it from the 401 response, which is how a client finds where to log in. The other 5 either use the older 2025-03-26 discovery layout or publish the metadata without pointing to it in the 401.
Client registration. The current spec says Dynamic Client Registration "is deprecated and retained for backwards compatibility with authorization servers that do not support Client ID Metadata Documents." 25 of 61 advertise Client ID Metadata Documents (CIMD). The other 36 rely on dynamic registration or manual client setup. Nothing breaks today, but every client that connects to those 36 still needs a registration step the spec is moving away from.
Issuer check. The spec says authorization servers SHOULD include the iss parameter in authorization responses (RFC 9207), and advertise it with authorization_response_iss_parameter_supported. It lets a client catch an OAuth mix-up attack, where a code from one authorization server is sent to another. 40 of 61 do not advertise it.
Scope hint. 22 of 61 give the client no hint about which scopes to request, neither in the 401 nor in scopes_supported. The client then has to guess, and guessing usually means asking for more than it needs.
Between October 26 and November 4, six changes showed up:
None of these companies told us about it, and we did not contact them. It is a sign the spec changes are being picked up, just not all at once.
Score is out of 100 and also includes transport and HSTS checks that are not shown as columns. "Discovery: partial" means the server uses the older discovery layout or does not point to its metadata from the 401.
| Company | Score | CIMD | iss (RFC 9207) | Scope hint | Discovery |
|---|---|---|---|---|---|
| Fireflies | 100 | yes | yes | yes | ok |
| Notion | 100 | yes | yes | yes | ok |
| Airtable | 98 | yes | no | yes | ok |
| Apollo | 98 | yes | no | yes | ok |
| Canva | 98 | yes | no | yes | ok |
| Clerk | 98 | yes | yes | yes | ok |
| Klaviyo | 98 | yes | yes | no | ok |
| Linear | 98 | yes | yes | yes | ok |
| Neon | 98 | yes | yes | no | ok |
| Railway | 98 | yes | yes | yes | ok |
| Sentry | 98 | yes | yes | yes | ok |
| Tavily | 98 | yes | yes | yes | ok |
| Vercel | 98 | yes | no | yes | ok |
| monday.com | 98 | yes | yes | no | ok |
| Amplitude | 96 | yes | no | yes | ok |
| Cal.com | 96 | yes | no | no | ok |
| Grafana | 96 | yes | no | yes | ok |
| Granola | 96 | yes | no | yes | ok |
| Honeycomb | 96 | yes | no | yes | ok |
| MongoDB | 96 | yes | yes | no | ok |
| PostHog | 96 | yes | no | yes | ok |
| Resend | 96 | yes | yes | no | ok |
| Todoist | 96 | yes | no | yes | ok |
| Figma | 95 | no | yes | yes | ok |
| GitHub | 95 | no | yes | yes | ok |
| Supabase | 95 | no | yes | yes | ok |
| Semgrep | 94 | yes | no | no | ok |
| Asana | 93 | no | no | yes | ok |
| Buffer | 93 | no | no | yes | ok |
| ClickUp | 93 | no | yes | yes | ok |
| Close | 93 | no | no | yes | ok |
| Gamma | 93 | no | yes | yes | ok |
| GitLab | 93 | no | no | yes | ok |
| Jam | 93 | no | no | yes | ok |
| Miro | 93 | no | no | yes | ok |
| Netlify | 93 | no | no | yes | ok |
| Slack | 93 | no | no | yes | ok |
| Stripe | 93 | no | no | yes | ok |
| Ahrefs | 91 | no | no | no | ok |
| Box | 91 | no | no | no | ok |
| Cloudflare Bindings | 91 | no | yes | no | ok |
| Datadog | 91 | no | no | no | ok |
| Dropbox | 91 | no | no | yes | ok |
| Hex | 91 | no | no | no | ok |
| HubSpot | 91 | no | no | no | ok |
| Intercom | 91 | no | no | yes | ok |
| Mux | 91 | no | no | no | ok |
| PagerDuty | 91 | no | no | yes | ok |
| Postman | 91 | no | no | no | ok |
| Prisma | 91 | no | no | yes | ok |
| Wix | 91 | no | no | yes | ok |
| Make | 90 | no | no | no | ok |
| PayPal | 90 | no | no | no | ok |
| Render | 90 | no | no | no | ok |
| Square | 90 | no | no | no | ok |
| Webflow | 90 | no | no | no | ok |
| Apify | 89 | yes | yes | yes | partial |
| Mercado Pago | 84 | no | yes | yes | partial |
| Zapier | 84 | no | no | yes | partial |
| Plaid | 82 | no | yes | no | partial |
| Atlassian | 80 | no | no | no | partial |
Notion and Fireflies passed every check.
Six more vendors answered tools/list without a token: Hugging Face, Context7, Shopify (setup.shopify.com), DeepWiki, Firecrawl and Browserbase. They are documentation, search and scraping tools where open access looks like a deliberate choice, so we left them out of the auth numbers. Nine addresses we tried did not answer as MCP servers, usually because we guessed the wrong URL, and they are not reported.
The three changes are small. Advertise client_id_metadata_document_supported once your authorization server supports CIMD, include iss in authorization responses and set authorization_response_iss_parameter_supported: true, and put a scope in the WWW-Authenticate header of the 401.
If you think we scored your server wrong, run it through the [checker](https://x1y1.co/mcp-check) and tell us at [hello@x1y1.co](mailto:hello@x1y1.co). We would rather fix a rule than publish a wrong number. There is also a JSON API: `https://x1y1.co/api/mcp-check?url=<server>`.
*Originally published at [x1y1.co](https://x1y1.co/journal/official-mcp-servers-auth-spec-check/).*