Implement SEP-1036: URL mode elicitation for secure out-of-band interactions #1580
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This commit adds support for URL mode elicitation as specified in SEP-1036,
enabling servers to direct users to external URLs for sensitive interactions
that must not pass through the MCP client.
Key changes:
Types (src/mcp/types.py):
- Add ELICITATION_REQUIRED error code (-32000)
- Update ElicitationCapability to support form and url modes
- Add ElicitTrackRequest and ElicitTrackResult for progress tracking
- Add UrlElicitationInfo and ElicitationRequiredErrorData types
- Update ElicitRequestParams with mode field and URL mode parameters
Server (src/mcp/server/):
- Add elicit_url() helper function in elicitation.py
- Add elicit_form() and elicit_url() methods to ServerSession
- Maintain backward compatibility with existing elicit() method
Client (src/mcp/client/session.py):
- Update capability negotiation for form and URL modes
- Add track_elicitation() method for progress monitoring
Tests:
- Comprehensive test coverage for URL mode elicitation
- Verify backward compatibility with form mode
- All 311 existing tests pass
Use cases enabled:
- OAuth authorization flows with third-party services
- Secure credential collection (API keys, passwords)
- Payment and subscription flows
- Any sensitive interaction requiring out-of-band handling
Breaking changes:
- ElicitRequestParams now requires mode field ("form" or "url")
- Clients must declare which elicitation modes they support
Closes: modelcontextprotocol/modelcontextprotocol#887
Remove unnecessary isinstance check for CancelledElicitation since type narrowing makes it redundant, and remove the unused import.
Add None check for requestedSchema before accessing properties to fix type narrowing error that was blocking CI.
maxisbey
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Summary
This PR implements SEP-1036 (URL mode elicitation) as specified in modelcontextprotocol/specification#887, adding support for secure out-of-band interactions that bypass the MCP client.
Note
SEP 1036 is currently Pending, so this feature should be considered experimental
Key Changes
Type System (
src/mcp/types.py):ELICITATION_REQUIREDerror code (-32000)ElicitationCapabilityto support bothformandurlmodesElicitTrackRequestandElicitTrackResultfor progress trackingUrlElicitationInfoandElicitationRequiredErrorDatatypesElicitRequestParamswithmodefield and URL mode parametersServer Implementation (
src/mcp/server/):elicit_url()helper function for URL mode elicitationelicit_form()andelicit_url()methods toServerSessionelicit()methodClient Implementation (
src/mcp/client/session.py):track_elicitation()method for monitoring URL mode progressTests (
tests/server/fastmcp/test_url_elicitation.py):Use Cases Enabled
This implementation enables servers to:
Breaking Changes
ElicitRequestParamsnow requires amodefield ("form" or "url")Testing
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