[md]MCP feature support
Targeting MCP spec 2025-11-25. The "Client support" column reflects the state of major clients (Claude Code, Claude Desktop, Cursor, opencode) per modelcontextprotocol.io/clients as of April 2026:
- Universal — all four
- Most — three of four
- Some — one or two
- Rare — niche/inconsistent
- None — no major client
| Feature | scala-mcp | Client support | Notes |
|---|---|---|---|
Tools (list / call) |
✅ | Universal | Includes structuredContent |
| Resources, subs, templates | ✅ | Most | Cursor doesn't expose resources |
| Prompts | ✅ | Universal | |
| Initialize / capabilities | ✅ | Universal | Required by spec |
| Ping | ✅ | Universal | Required by spec |
| Logging notifications | ✅ | Most | Accepted; rendering varies. logging/setLevel not yet |
| Elicitation | 🟡 | Some | Claude Code + Cursor. Form mode ✅, URL mode ❌ |
| Pagination | 🟡 | Universal | Cursors typed; server always returns nextCursor=None |
| Cancellation | ✅ | Most | notifications/cancelled cancels the in-flight fiber via per-session registry |
| Sessions (Streamable HTTP) | ✅ | Most | Mcp-Session-Id + auth-aware sessions |
MCP-Protocol-Version header |
❌ | Universal | Clients send it; we don't validate |
Progress (progressToken) |
❌ | Rare | Few clients emit the token |
_meta on requests/responses |
✅ | Universal | Builder API on every type; ToolMiddleware exposes request _meta to handlers |
| Sampling | 🟡 | None | Server→client plumbing via ServerRequester; no typed SamplingClient helper yet |
| Roots | 🟡 | Most | ClientHandler routes roots/list; no typed server-side helper. opencode lacks client support |
| Completion | ❌ | None | No client surfaces it |
| Tasks (experimental) | 🟡 | None | ToolExecution.taskSupport advertised; tasks/list / tasks/cancel not wired |
Tool/prompt list_changed |
✅ | Universal | Notifications wired via NotificationSink |
| 2025-11-25 metadata fields | ✅ | Some | title, icons, annotations, execution, _meta on tools; title/icons/annotations/_meta on resources; title/icons/_meta on prompts |