Issues authenticating with custom domain for MCP registry

[sarahwooders]

Describe the bug
We've followed the instructions here for registering an MCP server. We are using a custom domain to register the server, however are getting authentication issues:

To Reproduce
Steps to reproduce the behavior:

1. Follow custom domain instructions here
2. Try to authenticate with DNS mcp-publisher login dns --domain yourcompany.com --private-key $(openssl pkey -in key.pem -noout -text | grep -A3 "priv:" | tail -n +2 | tr -d ' :\n')

Expected behavior
We expect authentication to succeed.

Logs
Authentication error:

 > mcp-publisher login dns --domain letta.com --private-key $(openssl pkey -in key.pem -noout -text | grep -A3 "priv:" | tail -n +2 | tr -d ' :\n')  
 
Logging in with dns...
Error: failed to get token: failed to exchange dns signature: token exchange failed with status 401: {"title":"Unauthorized","status":401,"detail":"DNS authentication failed","errors":[{"message":"no valid MCP public keys found in DNS TXT records"}]}

We've also checked the TXT record:

 > dig TXT _mcp-registry.letta.com                                                                                                                                                               

;; ANSWER SECTION:
_mcp-registry.letta.com. 300	IN	TXT	"v=MCPv1; k=ed25519; p=...."

We waited about 2 hours for propagation so are still getting auth errors.

[domdomegg]

tldr: Instead of the subdomain _mcp-registry.letta.com, you should put the TXT record on letta.com.

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Apologies for the confusion here, and thanks for reporting! I think we explored a few different ways of doing this and forgot to update the docs when we switched from this subdomain to the root domain.

I've raised #388 to fix the docs.

Thanks again for being an early preview user and giving us this feedback 🙌