MCP elicitation UI

What the user sees when a server asks for input mid-tool-call

The Model Context Protocol lets a server pause a running tool call and send the client an elicitation/create request — a short message plus a JSON Schema of the fields it needs (a missing required value, a confirmation, which workspace to target). The client collects the input and returns accept / decline / cancel, and the server resumes. It's optional and server-initiated: the model never asks, the server interrupts.

On the current revision, 2026-07-28 (new in 2.0), the mechanics change but the experience doesn't. There's no open stream to push a request down, so the server ends the call with an input_required result that carries the same request. The client shows the same sheet, then sends the call again with the user's answer. A multi-step flow repeats this, and the client stops after 8 rounds. You're only asked once if you say no: Cancel ends the tool call there, and after Decline the sheet doesn't come back for that call even if the server asks again.

The SDK handles this in two layers. Core catches the request (off the tool-call stream, or from an input_required result on 2026-07-28), flattens the schema into typed fields, attaches the originating server's identity, and hands it to whatever MCPElicitationHandler the app registered — or auto-declines if there is none. Components ships a ready-made SwiftUI implementation of that handler so most apps don't build their own: a presenter plus the sheet below.

The sheet

What the built-in sheet does for you

• Names the server. The header is the connected server's own serverInfo.title, with a · not <your app> line — the spec requires clients to show which server is asking and forbids using elicitation to phish for credentials, so the framing is the SDK's, never the server's.
• Typed controls per field. string → text field; format: "date" → date picker; format: "email" / "uri" → text field with on-submit validation; number/integer with minimum and maximum → slider with a live readout, otherwise a field with the range as its placeholder; boolean → toggle; a single-value enum → a segmented control (up to three options) or a menu; an array of enum → a checkbox list.
• Humanized labels. assignee_email renders as "Assignee email" when the server gave no title; required fields get a *.
• Real submit validation. Errors appear per-field only after the first Submit attempt, not while the user is still typing.
• Only sends real answers. Fields the user never touched are dropped from the accept payload rather than sent as empty strings — the same rule Core applies to model-supplied tool arguments.
• Decline vs Cancel. Decline tells the server "I won't provide this"; Cancel (and Esc, and dragging the sheet away) means "I didn't decide" — two distinct responses the server can act on differently. On 2026-07-28, Cancel also ends the tool call, and after Decline a server that asks again is declined without the sheet reappearing. The model gets a short note saying the user cancelled or declined.
• Times out. An unanswered prompt auto-cancels after two minutes so a tool call can't hang forever waiting on a sheet nobody is looking at. On 2026-07-28 that ends the tool call like any other Cancel.

Try it

The MCP reference server exposes an elicitInputs tool that requests input with a mix of field types — the quickest way to see the sheet without touching a real account, right in LocalLM Lab itself, no code required:

Want to see it from the SDK side instead? None of the public example apps wire the presenter up yet (components-demo included) — the three lines it takes are in the SDK guide's §3c.

Contact

Questions, or building something with this? Contact neuron@thisbrain.ai or join our Discord.