Extension Support Matrix

This matrix shows which MCP clients support each official extension. Extensions are always opt-in: a client only uses an extension if both client and server declare support in the extensions field of their capabilities.

This list is maintained by the community. If you notice any inaccuracies or would like to add or update information, please submit a pull request.

Extension overview

Extension	Identifier	Description
MCP Apps	`io.modelcontextprotocol/ui`	Interactive HTML interfaces rendered inline in the conversation
OAuth Client Credentials	`io.modelcontextprotocol/oauth-client-credentials`	Machine-to-machine auth without interactive user login
Enterprise-Managed Authorization	`io.modelcontextprotocol/enterprise-managed-authorization`	Centralized access control via enterprise IdP
Skills over MCP	`io.modelcontextprotocol/skills`	Discover skills and read their instructions and supporting files

Support matrix

Client	MCP Apps	OAuth Client Credentials	Enterprise Auth	Skills
Claude (web)	✓
Claude Desktop	✓
VS Code GitHub Copilot	✓
Microsoft 365 Copilot	✓
Goose	✓
Postman	✓
MCPJam	✓
ChatGPT	✓			Partial
Cursor	✓
Archestra.AI	✓		✓
PostHog Code	✓
fast-agent				Partial
MCP Inspector				Partial
mcpc MCP CLI		✓	✓	✓

Auth extension support (OAuth Client Credentials and Enterprise-Managed Authorization) is tracked separately from the core MCP authorization features (DCR, CIMD). Check each extension’s specification and the ext-auth repository for the latest implementation status.

Adding extension support to your client

If you’re building an MCP client and want to implement extension support:

Review the extension specification (e.g., in the ext-auth or ext-apps repository)
Declare support in the extensions field of the io.modelcontextprotocol/clientCapabilities your client sends in each request’s _meta, and read the server’s extensions from its server/discover response
Implement the extension’s protocol requirements
Submit a pull request to update this matrix

See Extensions Overview for details on the capability negotiation mechanism.