This function sends a fax from a Zoho Creator record through the RingCentral API: it authenticates, caches the access token so you are not re-authenticating on every call, pulls a PDF from a Creator report, and posts it to RingCentral as a multipart request.

Before you start

• A RingCentral app in the developer console with the JWT auth flow enabled and fax permissions granted. Generate a JWT credential there.
• A Creator form named RC_Token with fields Access_Token (multi line), Expiry_Time (date-time), Added_User.
• A Zoho OAuth connection for pulling the report PDF, named creator_oauth_connection.
• Keep CLIENT_ID, CLIENT_SECRET and the JWT in Creator variables. They are shown inline below only so the example reads in one piece.

Deluge function

// ============================================
// RINGCENTRAL FAX FROM ZOHO CREATOR  (JWT auth)
// Standalone function. Call from a button or workflow.
// ============================================

void ringcentral.sendFax(string faxNumber, string coverText, int recordId)
{
    // --- Credentials. Store these as Creator variables, not inline. ---
    CLIENT_ID     = "YOUR_RINGCENTRAL_CLIENT_ID";
    CLIENT_SECRET = "YOUR_RINGCENTRAL_CLIENT_SECRET";
    JWT_CREDENTIAL = "YOUR_JWT_CREDENTIAL_FROM_THE_RC_CONSOLE";
    API_SERVER = "https://platform.ringcentral.com";

    // --- 1. Reuse a cached token if it is still good ---
    accessToken = "";
    cached = RC_Token[ID != null] sort by Added_Time desc range from 0 to 1;
    if(cached.count() > 0 && zoho.currenttime < cached.Expiry_Time)
    {
        accessToken = cached.Access_Token;
    }
    else
    {
        // --- 2. JWT bearer flow. Replaces the retired password grant. ---
        authHeaders = Map();
        authHeaders.put("Authorization","Basic " + zoho.encryption.base64Encode(CLIENT_ID + ":" + CLIENT_SECRET));
        authHeaders.put("Content-Type","application/x-www-form-urlencoded");

        authBody = Map();
        authBody.put("grant_type","urn:ietf:params:oauth:grant-type:jwt-bearer");
        authBody.put("assertion",JWT_CREDENTIAL);

        authResp = invokeurl
        [
            url    : API_SERVER + "/restapi/oauth/token"
            type   : POST
            parameters : authBody
            headers: authHeaders
        ];

        accessToken = authResp.getJSON("access_token");
        if(accessToken == null || accessToken == "")
        {
            info "RingCentral auth failed: " + authResp.toString();
            return;
        }

        expiresIn = authResp.getJSON("expires_in").toLong();
        delete from RC_Token[ID != null];
        insert into RC_Token
        [
            Added_User   = zoho.loginuser
            Access_Token = accessToken
            Expiry_Time  = zoho.currenttime.addSeconds(expiresIn - 300)
        ];
    }

    // --- 3. Fetch the PDF to fax, straight from Creator ---
    pdfFile = invokeurl
    [
        url  : "https://creatorapp.zohopublic.com/YOUR_ACCOUNT/YOUR_APP/report/Invoices/" + recordId + "/pdf"
        type : GET
        connection : "creator_oauth_connection"
    ];

    // --- 4. Send the fax. multipart/form-data, direct to RingCentral. ---
    faxHeaders = Map();
    faxHeaders.put("Authorization","Bearer " + accessToken);

    faxParams = Map();
    faxParams.put("to",faxNumber);
    faxParams.put("faxResolution","High");
    faxParams.put("coverIndex",0);
    faxParams.put("coverPageText",coverText);

    faxResp = invokeurl
    [
        url    : API_SERVER + "/restapi/v1.0/account/~/extension/~/fax"
        type   : POST
        parameters : faxParams
        files  : pdfFile
        headers: faxHeaders
    ];

    msgId = faxResp.getJSON("id");
    if(msgId != null)
    {
        info "Fax queued. Message id " + msgId + ", status " + faxResp.getJSON("messageStatus");
    }
    else
    {
        info "RingCentral fax error: " + faxResp.toString();
    }
}

Notes

• The token cache matters. RingCentral rate-limits the token endpoint hard. Authenticating on every fax will get you throttled. The RC_Token lookup re-uses a token until five minutes before it expires.
• from is not yours to set. RingCentral picks the sending fax number from the extension’s outbound fax settings. Passing a from in the request does nothing.
• Limits. 50 MB combined, 200 pages, and no special characters in attachment filenames — a filename with a comma or a slash will fail the whole request.
• Sandbox first. Swap API_SERVER for https://platform.devtest.ringcentral.com while you are testing. Sandbox faxes do not send and do not bill.