Deliver an MCP elicitation request in form or URL mode under the Multi Round-Trip Requests pattern

Documented steps

1. Read https://modelcontextprotocol.io/specification/2026-07-28/client/elicitation. Elicitation is no longer a server-initiated request; it arrives as an entry in InputRequiredResult.inputRequests.
2. Client: declare support per request in _meta['io.modelcontextprotocol/clientCapabilities'].elicitation, with 'form' and/or 'url' sub-keys. An empty object means form-only, for backward compatibility.
3. Server: return resultType 'input_required' with an inputRequests entry whose method is 'elicitation/create', plus a requestState you can resume from.
4. Form mode: set params.mode to 'form' (or omit it, since form is the default) and supply an optional 'requestedSchema' describing the fields to collect.
5. URL mode: set params.mode to 'url' and supply params.url. Data other than the URL is not exposed to the client.
6. Client: render the request, then return an ElicitResult inside inputResponses on the retry, using exactly one of three action values: 'accept', 'decline' or 'cancel'.
7. 'accept' means the user approved or submitted; include 'content' matching requestedSchema for form mode, and omit content for URL mode.
8. 'decline' means the user explicitly refused. 'cancel' means the user dismissed without an explicit choice — closed the dialog, pressed Escape, or the browser page failed to load. Content is typically omitted for both.
9. URL mode: show a consent UI before opening the URL, then retry the original request with {'action':'accept'} and the echoed requestState.
10. Server: on that retry, decide from your own requestState whether the out-of-band interaction actually completed; return the final result, or another InputRequiredResult to keep waiting.
11. Client: provide manual controls letting the user retry or cancel the original request while an out-of-band interaction is pending (spec: SHOULD).
12. Verify all three actions end-to-end, including a URL-mode flow where the user consents but the out-of-band step has not finished yet.