Why Muse connectors get rejected

What reviewers and the rules say

The server works for you but not from the reviewer’s network. Review traffic goes through TLS-inspecting proxies and automated clients, which fail on things a browser at home never hits: Encrypted ClientHello advertised in DNS (the proxy resets the handshake, so nothing reaches your logs), a firewall or bot rule that answers scripts with 403, a 403 instead of a 401 for calls without a token, or a URL pasted with a trailing slash that 404s. ECH alone cost one developer three ChatGPT rejections. OpenAI uses the same wording when the test credentials don’t work, so check sign-in too.

How to fix it

• Turn off Encrypted ClientHello for the MCP host. On Cloudflare it’s a zone setting, and only reachable through the API on the free plan.
• Let automated clients through on the MCP path: no bot challenge, no user-agent or country rules.
• Answer calls without a token with 401 and a WWW-Authenticate header, never 403.
• Serve /mcp/ as well as /mcp.
• Test from outside your own network, with a TLS 1.2 client as well as a browser.
• Appeal by replying to the rejection email with your case ID, and ask what error the reviewer saw.

How common it is: in our scan of Claude’s connector directory on 29 September, 16% of servers advertise Encrypted ClientHello in DNS (505 of 3,185), and 39% of servers stop working when the URL has a trailing slash (221 of 562).

Caught by

• server.ech DNS does not advertise Encrypted ClientHelloServer check
• server.bot-filter Automated clients are not blockedServer check
• auth.401 Unauthenticated calls get 401 with resource_metadataServer check
• server.trailing-slash The URL with a trailing slash works tooServer check
• server.reachable Server answersServer check
• server.tls12 A TLS 1.2 client can connectmcplane CLI

Check your servermcplane docs

What reviewers and the rules say

Reviewers sign in as strangers, on a network you don’t control, with the account you gave them. It breaks when the account needs an emailed code, a magic link, MFA or a Google login, when the sign-in page waits on JavaScript from another domain that is slow or blocked (they see a blank page), when that domain sits behind a bot challenge, or when OAuth discovery or client registration fails.

How to fix it

• Give reviewers a dedicated account with a login and password that works immediately: no MFA, no email or SMS codes, no magic links, not your Google or SSO login, and seeded with data for every test case.
• Sign in once as a brand-new user, in a fresh browser, from outside your network. Make the page show something before any JavaScript loads.
• Keep bot challenges off your sign-in and auth domains, not just the MCP path.
• Serve protected-resource metadata on the MCP host, authorisation-server metadata and PKCE (S256), and Dynamic Client Registration that accepts the store’s redirect URIs.
• Accept private-use redirect schemes such as cursor:// in client registration, or desktop clients can’t sign in at all.

Caught by

• auth.prm Protected-resource metadata resolves on the MCP hostServer check
• auth.as-metadata Authorization-server metadata resolvesServer check
• auth.pkce PKCE (S256) is supportedServer check
• auth.dcr Dynamic Client Registration is offeredServer check
• auth.dcr-native Registration accepts native redirect URIs (with --register)mcplane CLI
• A reviewer account a stranger can use, and a sign-in page that renders without third-party scriptsBy hand

Check your servermcplane docs

What reviewers and the rules say

Every store asks for a privacy policy, and reviewers read it. Anthropic wants it to cover data collection, usage and storage, third-party sharing, retention and contact information. OpenAI asks for the categories of personal data you collect, why you use them, who receives them, how long you keep them and what users can do about it. Data your tools return that the policy doesn’t mention counts as a gap.

How to fix it

• Link a page that loads without signing in.
• Cover collection, use, sharing, retention, user controls such as deletion, and how to contact you.
• Mention the data your tools return and any free-form content users send, not only what they type into forms.

How common it is: in our scan of Claude’s connector directory on 29 September, 4% of servers link a privacy policy that doesn’t load (145 of 3,283).

Caught by

• listing.privacy The privacy policy covers what reviewers look forServer check
• listing.privacy-content Free-form content is covered by the privacy policyServer check

Check your servermcplane docs