Elicitation

This guide explains how a client handles elicitation requests sent by the MCP server.

The Client Drives the Round-Trips

Under MCP 2026-07-28 elicitation is not a push request the client receives out of band. The server answers a tool call with input_required; the client's handler produces the answer and re-issues the call, carrying the sealed requestState back.

Neva does that loop for you, inside client.tools().call(..):

• your handler is invoked once per input_required round;
• client.tools().call returns only the final result — the caller sees a single call;
• registering a handler is what makes the client declare clientCapabilities.elicitation, and a server may only ask for a kind the client declared;
• cap the re-issues per slot with McpOptions::with_max_mrtr_rounds.

Enabling Elicitation Support

let mut client = Client::new()
    .with_options(|opt| opt
        .with_elicitation(|e| e
            .with_form()
            .with_url()));

This enables:

• Form-based elicitation
• URL elicitation

Handling Elicitation Requests

Define an elicitation handler using the #[elicitation] attribute macro.

#[json_schema(ser)]
struct Contact {
    name: String,
    email: String,
    age: u32,
}

#[elicitation]
async fn elicitation_handler(params: ElicitRequestParams) -> ElicitResult {
    match params {
        ElicitRequestParams::Url(url) => {
            // Follow the url to perform the external action.

            ElicitResult::accept()
        }
        ElicitRequestParams::Form(form) => {
            // Show the form to a user to fill in the data

            let contact = Contact {
                name: "John".to_string(),
                email: "john@email.com".to_string(),
                age: 30,
            };

            elicitation::Validator::new(form)
                .validate(contact)
                .into()
        }
    }
}

A handler need not be async

Client::map_elicitation and #[elicitation] accept a plain fn returning an ElicitResult directly. A handler that puts a blocking dialog in front of a user — a terminal prompt, a native modal — is exactly what #[elicitation(blocking)] is for: it runs on Tokio's blocking pool instead of holding a runtime worker for as long as the person takes to answer. The same applies to #[sampling] and Client::map_sampling. See Handler shapes.

What Happens Here?

• URL elicitation
  • Client accepts and performs the action externally
• Form elicitation
  • Client constructs data
  • Data is validated against the server schema
  • Validated payload is returned as ElicitResult

info

If you skip the with_elicitation() or with_form() or with_url() but declare the elicitation handler this will enable form elicitation by default.

Elicitation Completion

Removed in MCP 2026-07-28

There is no notifications/elicitation/complete any more — answering the input request is the completion signal, so Client::on_elicitation_completed and ElicitationCompleteParams no longer exist. URL elicitation also lost its elicitationId: with no server-initiated completion signal there is nothing to correlate.

If you were using the notification for UI updates or audit logging, hook the handler itself instead — it runs exactly when the client answers.

These APIs come back under legacy-spec.

Learn By Example

A complete working example is available here.