feat: expose Sanity MCP on MCP Registry

[jonahsnider]

Closes AIGRO-4176

Since the MCP repo is closed source I opted to add this functionality to agent-toolkit. Once merged, we can trigger releases to the MCP Registry from GitHub Actions using their workflow_dispatch functionality.

The server.json is currently setup with a name of io.github.sanity-io/mcp - AFAIK this means we can publish without needing to prove DNS or HTTPS ownership of sanity.io. I think we can change this in the future if needed?
server.json has a name of io.sanity/mcp, which requires us to prove we own sanity.io -- see sanity-io/www-sanity-io#3295

Here's some resources to add context during review:

• Perplexity's MCP, which is listed on the registry - GitHub Actions CD and server.json
• Registry docs

[jonahsnider]

• feat: expose Sanity MCP on MCP Registry #19 👈 (View in Graphite)
• ci: add GitHub Actions CI for validating skills #18
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[jwoods02]

Thanks for picking this up, love adding this to a GH action.

I'd recommend we use io.sanity/mcp as the name from the start rather than io.github.sanity-io/mcp. Per the registry docs on verifying server authenticity (https://modelcontextprotocol.io/registry/about#verifying-server-authenticity), the namespace is how the registry establishes trust — domain-verified names (io.sanity/) signal this is officially from Sanity, while GitHub-based names (io.github.sanity-io/) are the convention for individual devs or projects without domain verification.

Changing the name later would effectively create a new server in the registry (it's the unique identifier), so it's worth getting right up front.

The publish workflow will also need to switch from github-oidc auth to DNS or HTTP auth, but should be a relatively easy change, just needs the private key stored as a GitHub Actions secret.

[jonahsnider]

I'd recommend we use io.sanity/mcp as the name from the start

done 🫡 - see sanity-io/www-sanity-io#3295 for the PR to add the proof file to sanity.io

[jonahsnider]

Superseded by sanity-io/mellon#275