registry/docs/reference/api/extensions.md
Tadas Antanavicius fdcb38537f
Update OpenAPI spec to use v0.1 endpoints and make _meta optional (#811)
Prepared by Claude Code, reviewed by me.

## Summary
- Update all API endpoint paths from `/v0/` to `/v0.1/` in the OpenAPI
spec
- Bump OpenAPI spec version from `2025-10-17` to `2025-12-01` (in `$id`
and `info.version`)

## Rationale
This ensures sub-registries implementing the spec are adhering to the
stable v0.1 version rather than the unstable v0. The API freeze (v0.1)
provides stability guarantees that sub-registries need.

## Additional cleanup

### Make `_meta` optional in `ServerResponse`

The `_meta` field (and its `io.modelcontextprotocol.registry/official`
extension) were never intended to be required parts of the spec.
Sub-registries may not use these registry-specific metadata fields, so
they should be optional.

### Move extensions docs to use /v0.1/ instead of /v0/

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude <noreply@anthropic.com>
2025-12-10 23:58:01 +02:00

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2.6 KiB
Markdown

# Registry Extensions Specification
A standardized way for registries to provide experimental or community-driven features without committing them to the core API specification.
## Motivation
[The core generic registry API](./generic-registry-api.md) intentionally stays minimal to ensure stability and broad adoption. Extensions provide a path for:
- **Experimentation**: Try new features without core API changes
- **Community innovation**: Anyone can implement custom extensions
- **Gradual adoption**: Popular extensions may inform future core API features
- **Avoiding breaking changes**: Failed experiments can be deprecated without API versioning churn
## URL Structure
Extensions live under the `/v0.1/x/` prefix:
```
/v0.1/x/<namespace>/<extension>[/<path>]
```
**Components:**
- `<namespace>`: Reverse domain ownership (e.g., `com.example`, `io.github.username`)
- `<extension>`: Extension name (lowercase, hyphens for word separation)
- `<path>`: Extension-specific path structure (optional)
**Examples:**
```
/v0.1/x/com.example/search?q=database
/v0.1/x/com.example/stats
/v0.1/x/io.github.username/custom-feature
```
## Conventions
Where possible:
- Follow standard REST conventions, return simple JSON responses, and avoid special headers
- For list endpoints, use cursor-based pagination matching the core API
- Extensions requiring authentication **SHOULD** follow the [Registry Authorization Specification](./registry-authorization.md)
- Build open-source implementations in a composable way on top of the core APIs (e.g. as opposed to via custom database integration)
## Implementation Requirements
Registries implementing extensions **SHOULD** namespace extensions properly to avoid conflicts.
Clients consuming extensions **MUST** gracefully handle missing extensions.
## Example
A simple server stats extension:
```bash
GET /v0.1/x/com.example/stats
```
```json
{
"totalServers": 1234,
"totalVersions": 5678,
"recentPublishes": 42
}
```
## Future Considerations
- **Extension discovery**: A potential `/v0.1/x` endpoint to list available extensions
- **Extension metadata**: Standardized metadata format for extension capabilities
- **Defining common extensions**: Like semantic conventions from OpenTelemetry, develop common extensions that registries can adopt (possibly under an experimental namespace)
- Search extension for free-text search across server metadata ([#389](https://github.com/modelcontextprotocol/registry/issues/389))
- MCP server extension to expose the registry itself as an MCP server for programmatic access ([#24](https://github.com/modelcontextprotocol/registry/issues/24))