Magento 2: How To Create Product Problematically Using Custom Rest API

I need to create a product using a custom Rest API. (this is my first time working on API). So to check API whether it’s working or not I wrote the code below, API is working, now I need to give different parameters to create a simple product but I am not able to figure out how to do that. If you know how to do that please help me out.

app/code/Webkul/Marketplace/etc/webapi.xml

<?xml version="1.0"?>
<routes xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../app/code/Magento/Webapi/etc/webapi.xsd">
    <route method="POST" url="/V1/custom/custom-api/">
        <service class="WebkulMarketplaceApiCustomInterface" method="getPost"/>
        <resources>
            <resource ref="anonymous"/>
        </resources>
    </route>
</routes>

app/code/Webkul/Marketplace/etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="WebkulMarketplaceApiCustomInterface" type="WebkulMarketplaceModelApiCustom"/>
</config>

app/code/Webkul/Marketplace/Api/CustomInterface.php

<?php

namespace WebkulMarketplaceApi;
interface CustomInterface
{
    /**
     * GET for Post api
     * @param string $value
     * @return string
     */
    public function getPost($value);
}

app/code/Webkul/Marketplace/Model/Api/Custom.php

<?php
namespace WebkulMarketplaceModelApi;

use PsrLogLoggerInterface;
class Custom
{
    protected $logger;
    public function __construct(
        LoggerInterface $logger
    )
    {
        $this->logger = $logger;
    }
    /**
     * @inheritdoc
     */
    public function getPost($value)
    {
        $response = ['success' => false];
        try {
            $response = ['success' => true, 'data' => $value];
        } catch (Exception $e) {
            $response = ['success' => false, 'message' => $e->getMessage()];
            $this->logger->info($e->getMessage());
        }
        $returnArray = json_encode($response);
        return $returnArray; 
   }
}