The short answer is:
Yes, you absolutely can and should create all the necessary Facebook tracking data in HubSpot via the API to account for your Click-to-Chat campaigns.
The direct solution is to use the HubSpot Contacts API to create or update the contact record and manually populate the HubSpot ad-tracking fields, such as `utm_source` and `hsa_ad`, with the data you capture from your WhatsApp platform, mirroring the exact format HubSpot uses for website visits.
However, a more robust solution for future reporting is to use the HubSpot API in conjunction with the Facebook Conversions API for full-circle tracking, which accurately attributes the lead event directly to Facebook’s side as well 
The long answer is:
Your challenge is a very common one for businesses running non-website conversion paths like Facebook Click-to-Chat or Lead Ads.
Since the user interaction bypasses the standard HubSpot tracking script that automatically reads the URL parameters like `hsa_ad`, you must simulate that step using the HubSpot Contacts API.
Your WhatsApp platform is already capturing the crucial piece of data: the Facebook Ad ID.
You should take that Ad ID, along with static values for the other required tracking fields like `utm_source`=facebook, `utm_medium`=paid, `hsa_net`=facebook, and the relevant campaign, ad set, and account IDs, and map them to their corresponding custom or default HubSpot properties via the Contacts API when creating or updating the contact record.
This ensures that the contact in HubSpot looks exactly like a lead that came from a website visit, allowing your HubSpot reports, workflows, and lead source tracking to function correctly.
The HubSpot API is a flexible tool that lets you set any property value, including the ones it usually populates itself.
However, a better solution involves an extra step using the Facebook Conversions API (CAPI) alongside the HubSpot API, managed through an intelligent server-side pipeline like Google Tag Manager and a tool like Stape or Google Cloud Platform (GCP).
The better solution works like this: when the lead is successfully created in your WhatsApp platform, you first use the HubSpot API to create the contact and populate all the tracking properties, as described above.
Next, your server-side environment immediately sends an `Lead` or `Contact` Standard Event back to Facebook via the Conversions API.
This event includes the necessary customer information (like phone number or email, hashed for privacy) and the `Ad ID` the lead came from.
This two-way communication is superior because it not only enriches the contact in HubSpot but also closes the loop on Facebook’s side, giving the Facebook ads algorithm the necessary attribution signal to optimize your campaign performance, which is something simply populating the HubSpot fields cannot achieve 
This method provides accurate tracking on both platforms, resolving your core problem while improving your ad performance.
This comment was generated with the assistance of an AI tool, incorporating my expertise in conversion tracking 