Method Elicit

mcp/server.go:1239–1307

Elicit sends an elicitation request to the client asking for user input.

(ctx context.Context, params *ElicitParams)

// Elicit sends an elicitation request to the client asking for user input.
func (ss *ServerSession) Elicit(ctx context.Context, params *ElicitParams) (*ElicitResult, error) {
	if err := ss.checkInitialized(methodElicit); err != nil {
		return nil, err
	}
	if params == nil {
		return nil, fmt.Errorf("%w: params cannot be nil", jsonrpc2.ErrInvalidParams)
	}

	if params.Mode == "" {
		params2 := *params
		if params.URL != "" || params.ElicitationID != "" {
			params2.Mode = "url"
		} else {
			params2.Mode = "form"
		}
		params = &params2
	}

	if iparams := ss.InitializeParams(); iparams == nil || iparams.Capabilities == nil || iparams.Capabilities.Elicitation == nil {
		return nil, fmt.Errorf("client does not support elicitation")
	}
	caps := ss.InitializeParams().Capabilities.Elicitation
	switch params.Mode {
	case "form":
		if caps.Form == nil && caps.URL != nil {
			// Note: if both 'Form' and 'URL' are nil, we assume the client supports
			// form elicitation for backward compatibility.
			return nil, errors.New(`client does not support "form" elicitation`)
		}
	case "url":
		if caps.URL == nil {
			return nil, errors.New(`client does not support "url" elicitation`)
		}
	}

	res, err := handleSend[*ElicitResult](ctx, methodElicit, newServerRequest(ss, orZero[Params](params)))
	if err != nil {
		return nil, err
	}

	if res.Action != "accept" {
		return res, nil
	}

	if params.RequestedSchema == nil {
		return res, nil
	}
	schema, err := validateElicitSchema(params.RequestedSchema)
	if err != nil {
		return nil, err
	}
	if schema == nil {
		return res, nil
	}

	resolved, err := schema.Resolve(nil)
	if err != nil {
		return nil, err