I have an standard einstein bot that is calling an apex class. That apex class must accept a list of objects as input, and a string as output (with the value the the one in the first object of the list, in its field answer__c). The class is:

public with sharing class GetKnowledgeAnswer {
    @InvocableVariable(label='Input Object List' required=true)
    public List<sObject> knowledgeSearchResults;
    @InvocableVariable(label='Output Answer String' required=false)
    public String answer;

    @InvocableMethod(label='Get Knowledge Answer')
    public static List<GetKnowledgeAnswer> getAnswerFromKnowledge(List<GetKnowledgeAnswer> invokers) {
        for (GetKnowledgeAnswer invoker : invokers) {
            if (invoker.knowledgeSearchResults != null && !invoker.knowledgeSearchResults.isEmpty()) {
                Object firstObject = invoker.knowledgeSearchResults[0];
                if (firstObject instanceof Knowledge__kav) {
                    Knowledge__kav knowledgeObj = (Knowledge__kav) firstObject;
                    invoker.answer = knowledgeObj.Answer__c;
                } else {
                    invoker.answer = 'El primer objeto en la lista no es de tipo Knowledge__kav.';
            } else {
                invoker.answer = 'La lista de objetos está vacía o es nula.';
        return invokers;

Regarding the bot, that contains all the logic for the business process, the conflicting steps are:

Search knowledge matches:

search knowledge matches

Get answer from first match:

get answer from first match

When previewing the bot, it throws an error when calling the apex class:

Error: Error when invoking /support/conversations/0X909000000xlNF/invocations/0SC09000000xnyMGAQ: [{"actionName":"GetKnowledgeAnswer","errors":[{"statusCode":"REQUIRED_FIELD_MISSING","message":"Missing required input parameter: knowledgeSearc

Why does it say "REQUIRED_FIELD_MISSING"? I'm clearly passing the output from the previous step as input for the apex class. Wondering if previous block gives List<Object> but apex class expects List<sObject>? I'm totally blocked in here, any help would be much appreciated.

  • Did you find any solution to this. I am also struggling in a similar use case wherein i want to search from only a subset of knowledge articles . Since Knowledge Object search does not have a OOTB filter, i thought of taking the list returned by the object search and filter it in apex.
    – starhunter
    Apr 10, 2023 at 18:09

1 Answer 1


I've got quite same situation with using List variables between Bot and Apex. I decided just to use String variables in Bot and Json.serialize/deserialize combination in Apex.

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