MCP Python SDK 1.23.0 introduced automatic DNS rebinding protection that
auto-enables when host="127.0.0.1" (the default). This breaks containerized
deployments (Kubernetes, Docker) because the protection rejects requests
with Host headers like "nextcloud-mcp-server.default.svc.cluster.local:8000".
Root cause:
- FastMCP defaults to host="127.0.0.1"
- SDK auto-enables DNS rebinding protection with allowed_hosts=["127.0.0.1:*", "localhost:*", "[::1]:*"]
- K8s/Docker requests use service DNS names or proxied hostnames
- Protection middleware rejects these requests (421 Misdirected Request)
Solution:
- Explicitly pass transport_security=TransportSecuritySettings(enable_dns_rebinding_protection=False)
- Applied to all three FastMCP initializations (OAuth, Smithery, BasicAuth)
- DNS rebinding attacks mitigated by OAuth authentication and network isolation
This fixes issue #373 and enables MCP 1.23.x upgrade in PR #382.
For detailed analysis, see docs/MCP-1.23-DNS-REBINDING-FIX.md
Address all reviewer comments from PR #387:
1. ✅ Add unit tests for annotations (tests/server/test_annotations.py)
- 10 comprehensive test functions validating all annotation patterns
- Tests for titles, read-only, destructive, idempotent operations
- Validates specific ADR-017 decisions (webdav write, semantic search)
- Cross-category consistency checks
2. ✅ Fix nc_webdav_write_file idempotency classification
- Changed from idempotentHint=False to idempotentHint=True
- Rationale: Uses HTTP PUT without version control
- Writing same content to same path = same end state (idempotent)
3. ✅ Fix semantic search openWorldHint inconsistency
- Changed from openWorldHint=False to openWorldHint=True
- Rationale: Consistent with other Nextcloud tools
- Nextcloud is external to MCP server (indexed data is implementation detail)
4. ✅ Update ADR-017 with resolved decisions
- Converted Open Questions to Resolved Questions
- Added detailed rationale for webdav write and semantic search
- Updated status from Proposed to Implemented
- Added decision timeline with dates
5. ✅ Add MCP Tool Annotations guidelines to CLAUDE.md
- Comprehensive section with code examples for all patterns
- Key principles documented (idempotency, destructive, open world)
- References ADR-017 for detailed rationale
All OAuth tools verified to have proper annotations (oauth_tools.py lines 686-751).
Fixed 8 type checker errors across the codebase:
- vector/scanner.py: Handle None scroll results with null-safe iteration
- search/{bm25_hybrid,semantic}.py: Add None checks for result.payload
- auth/{unified_verifier,webhook_routes}.py: Assert non-None auth credentials
- client/webdav.py: Add None checks before int() conversions
- providers/openai.py: Assert embedding_model is not None
- search/algorithms.py: Explicitly type doc_types set and cast values
- observability/logging_config.py: Match parent class signature (log_data)
Also fixed test_create_tag_creates_system_tag to match WebDAV implementation
(was testing OCS API endpoint, now tests correct WebDAV endpoint with
Content-Location header).
Type checker: 0 errors (down from 8), 20 warnings (ignored)
Tests: All 192 unit tests passing
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
