The MCP Registry rejects our `server.json` remote because the URL uses
`{coder_url}` as the entire base. Registry validation requires remote
URLs to literally begin with `https://`, and template variables are only
allowed after the scheme/host. The previous value
(`{coder_url}/api/experimental/mcp/http`) fails both the JSON schema
`^https?://[^\s]+$` pattern and the semantic remote-URL check.
## Changes
- Use `https://{coder_hostname}/api/experimental/mcp/http` with a
`coder_hostname` variable (users now enter a hostname like
`coder.example.com` instead of a full URL).
- Update the VS Code registry instructions in
`docs/ai-coder/mcp-server.md` to ask for the deployment hostname.
Verified with `mcp-publisher validate` against
`registry.modelcontextprotocol.io`:
```
Validating against https://registry.modelcontextprotocol.io...
✅ server.json is valid
```
This was caught by running the `Publish to MCP Registry` workflow in
validate-only mode (`publish: false`) before any real publish, so
nothing broken reached the public registry.
<details>
<summary>Root cause detail</summary>
The registry validator (`internal/validators`) substitutes known
template variables, then parses the URL. Because `{coder_url}` replaces
the whole scheme+host, the parsed URL has no scheme and is rejected as
an invalid remote URL. Hard-coding `https://` and scoping the variable
to the host satisfies both the schema pattern and `IsValidRemoteURL`
(which also requires `https`). The registry mandates `https` for remotes
regardless, so there is no loss of functionality.
</details>
---
_Generated with Coder Agents._
## Summary
This adds the necessary configuration to publish Coder's remote MCP
server to the official MCP Registry at registry.modelcontextprotocol.io.
## Changes
- **`server.json`**: MCP server metadata for registry discovery
- **`.github/workflows/publish-mcp-registry.yaml`**: GitHub Actions
workflow to automatically publish on release
## How it works
1. When a new Coder release is published, the workflow automatically
publishes to the MCP Registry
2. MCP clients (Claude, ChatGPT, VS Code, etc.) can discover Coder via
the registry
3. Users just need to provide their Coder deployment URL - OAuth handles
authentication automatically via RFC 7591 Dynamic Client Registration
## MCP Registry Entry
The server will be listed as `io.github.coder/coder` with:
- **Transport**: `streamable-http`
- **Endpoint**: `{coder_url}/api/experimental/mcp/http`
- **Auth**: OAuth2 (automatic via
`/.well-known/oauth-authorization-server`)
## Testing
After merge and next release, verify at:
```bash
curl "https://registry.modelcontextprotocol.io/v0.1/servers?q=io.github.coder"
```
Closes#21275
---
_Generated with `mux` • Model: `anthropic:claude-opus-4-5` • Thinking:
`medium`_
---------
Co-authored-by: Ben Potter <me@bpmct.net>
Ben Potter