WhatsApp error 131008 (required parameter is missing): find the field your request left out

WhatsApp error 131008 tells you that your request was incomplete. Meta's error codes page describes it as "The request is missing a required parameter" and the listed solution is to "See the endpoint's reference to determine which parameters are required." It is always something in your own request body, so it is one of the quickest errors to fix once you know which field is gone. The message was rejected before sending, so the customer received nothing and nothing was charged.

Where it comes from

Every Cloud API endpoint has required parameters. For sending, the endpoint is POST /{phone-number-id}/messages, and a valid body needs at least messaging_product set to whatsapp, the recipient in to, a type, and an object whose key matches that type. A template message also needs a name and a language with a code. When any of these is absent, Meta stops before checking anything else and returns 131008.

The same code appears on other endpoints too, for example uploading media without messaging_product, or registering a phone number without the pin. The pattern is the same: a field the endpoint insists on was not there.

The fields most often missing

A missing template body variable is a slightly different case. When the number of parameters does not match the template, Meta usually returns 132000 instead. Our guide to sending a template message through the API shows how the components fit together.

What the error looks like

The response comes back immediately. Values and wording illustrative:

{
  "error": {
    "message": "(#131008) Required parameter is missing",
    "type": "OAuthException",
    "code": 131008,
    "error_data": {
      "messaging_product": "whatsapp",
      "details": "Parameter 'language' is required."
    },
    "fbtrace_id": "AqZ71bN0cRk3xTyLv5Hm2pW"
  }
}

The details string is the useful part. Log it with the request body (with personal data masked) so the developer sees both together.

Step-by-step fix

1. Read error_data.details. In most cases it names the field. If it does not, compare your body with the endpoint reference line by line.
2. Print the exact JSON you sent. Not the object before serialisation: the final string. Fields set to undefined in JavaScript vanish from JSON.stringify, which is a frequent cause.
3. Check the top level first: messaging_product, to, type.
4. Check that the object key matches type. type: "image" needs an image object; type: "template" needs a template object.
5. For templates, check name and language.code, then check that every component the template defines (header media, body variables, dynamic button URLs) is present.
6. Send again. Nothing was delivered the first time, so there is no risk of a duplicate.

Here is a template request that failed with 131008 because the language was missing, and the corrected version:

{
  "messaging_product": "whatsapp",
  "to": "919812345678",
  "type": "template",
  "template": {
    "name": "appointment_reminder"
  }
}

{
  "messaging_product": "whatsapp",
  "to": "919812345678",
  "type": "template",
  "template": {
    "name": "appointment_reminder",
    "language": { "code": "en" },
    "components": [
      {
        "type": "body",
        "parameters": [
          { "type": "text", "text": "Arjun" },
          { "type": "text", "text": "Thu 6 Nov, 11:30 am" }
        ]
      }
    ]
  }
}

A worked example

Sunrise Clinic in Pune sends appointment reminders from its practice software through a small Node service. After a code change, every reminder for the next morning fails with 131008. The developer reads details and sees the template language is missing: a refactor renamed the config key from lang to language, so the value read from the config is undefined and JSON.stringify drops the whole field.

He fixes the key, adds a check that refuses to send a template without language.code, and resends the evening's batch. Patients get their reminders a little later than planned, and nobody gets a duplicate, because the failed calls had never been sent.

Preventing 131008

• Validate before you call Meta. A schema (Zod, Joi, JSON Schema) for each message type you send catches empty to or missing language in your own logs instead of Meta's.
• Never let undefined reach the payload. Default or reject missing values explicitly.
• Keep template definitions in sync. If a template has an image header, your sender must always add the header component. Re-read the template from WhatsApp Manager when it is edited.
• Reject contacts without a number at import time, not at send time.
• Write one tested builder per message type instead of hand-writing JSON in many places.

How Broadchat shows 131008

Broadchat builds the request body for you from the template you pick and the variables you map, so required fields such as messaging_product, language and the header component come from the approved template itself. If Meta still rejects a send with 131008, the failed message shows the reason "A required parameter is missing." together with Meta's own text. When the missing piece is a media ID Meta no longer accepts, Broadchat uploads the file again and retries, and if that fails it sends the media by link.

For the closely related invalid-value error, see WhatsApp error 131009. The full list is in the WhatsApp API error codes cheat-sheet, and the template basics in the WhatsApp message templates guide. Agencies can give clients a no-code template sender under their own brand with the white-label program.