curl --request POST \
  --url https://api.flow.engineer/v1/messages \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "sender": "snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T",
  "to": {
    "phone": "+919812345678"
  },
  "content": {
    "type": "template",
    "template_id": "tpl_01JB8Z9X2D4F6H8K0M2P4R6T8V",
    "language": "en",
    "params": {
      "body": [
        "Asha",
        "order 1042"
      ]
    }
  }
}
'

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    sender: 'snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T',
    to: {phone: '+919812345678'},
    content: {
      type: 'template',
      template_id: 'tpl_01JB8Z9X2D4F6H8K0M2P4R6T8V',
      language: 'en',
      params: {body: JSON.stringify(['Asha', 'order 1042'])}
    }
  })
};

fetch('https://api.flow.engineer/v1/messages', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.flow.engineer/v1/messages"

payload = {
    "sender": "snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T",
    "to": { "phone": "+919812345678" },
    "content": {
        "type": "template",
        "template_id": "tpl_01JB8Z9X2D4F6H8K0M2P4R6T8V",
        "language": "en",
        "params": { "body": ["Asha", "order 1042"] }
    }
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.flow.engineer/v1/messages"

	payload := strings.NewReader("{\n  \"sender\": \"snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T\",\n  \"to\": {\n    \"phone\": \"+919812345678\"\n  },\n  \"content\": {\n    \"type\": \"template\",\n    \"template_id\": \"tpl_01JB8Z9X2D4F6H8K0M2P4R6T8V\",\n    \"language\": \"en\",\n    \"params\": {\n      \"body\": [\n        \"Asha\",\n        \"order 1042\"\n      ]\n    }\n  }\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

{
  "id": "msg_01JB8ZD4M6P8R0T2V4X6Z8B0C2",
  "conversation": "conv_01JB8ZC3K5M7P9R1T3V5X7Z9B1",
  "direction": "in",
  "status": "received",
  "content": {
    "type": "text",
    "text": "<string>",
    "format": "plain"
  },
  "livemode": true,
  "created_at": "2023-11-07T05:31:56Z",
  "delivered_as": {
    "type": "text",
    "reason": "<string>"
  },
  "error": {
    "type": "invalid_request",
    "message": "<string>",
    "hint": "Send a template instead: POST /v1/messages with content.type=template.",
    "doc_url": "https://api.flow.engineer/docs/errors/outside_window",
    "param": "<string>",
    "retry_after": 1,
    "conversation": "conv_01JB8ZC3K5M7P9R1T3V5X7Z9B1",
    "sender": "snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T",
    "channel_code": "<string>",
    "request_id": "<string>"
  },
  "channel_message_id": "<string>",
  "reply_to": "msg_01JB8ZD4M6P8R0T2V4X6Z8B0C2",
  "metadata": {},
  "updated_at": "2023-11-07T05:31:56Z"
}

{
  "error": {
    "type": "invalid_request",
    "message": "limit must be between 1 and 100.",
    "hint": "Pass limit between 1 and 100 (default 20), and page with after or before.",
    "doc_url": "https://api.flow.engineer/docs/errors/invalid_request",
    "param": "limit"
  }
}

{
  "error": {
    "type": "authentication",
    "message": "No valid API key was given.",
    "hint": "Send the header Authorization: Bearer fk_test_... (or fk_live_...); no key yet? Get a test key with curl -X POST https://api.flow.engineer/v1/sandbox/keys",
    "doc_url": "https://api.flow.engineer/docs/errors/authentication"
  }
}

{
  "error": {
    "type": "invalid_request",
    "message": "<string>",
    "hint": "Send a template instead: POST /v1/messages with content.type=template.",
    "doc_url": "https://api.flow.engineer/docs/errors/outside_window",
    "param": "<string>",
    "retry_after": 1,
    "conversation": "conv_01JB8ZC3K5M7P9R1T3V5X7Z9B1",
    "sender": "snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T",
    "channel_code": "<string>",
    "request_id": "<string>"
  }
}

{
  "error": {
    "type": "invalid_request",
    "message": "<string>",
    "hint": "Send a template instead: POST /v1/messages with content.type=template.",
    "doc_url": "https://api.flow.engineer/docs/errors/outside_window",
    "param": "<string>",
    "retry_after": 1,
    "conversation": "conv_01JB8ZC3K5M7P9R1T3V5X7Z9B1",
    "sender": "snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T",
    "channel_code": "<string>",
    "request_id": "<string>"
  }
}

{
  "error": {
    "type": "outside_window",
    "message": "Last message from the contact was 31h ago; WhatsApp allows only templates now.",
    "hint": "Send a template instead: POST /v1/messages with content.type=template.",
    "doc_url": "https://api.flow.engineer/docs/errors/outside_window",
    "conversation": "conv_01JB8ZC3K5M7P9R1T3V5X7Z9B1"
  }
}

{
  "error": {
    "type": "unsupported_content",
    "message": "iMessage cannot show buttons.",
    "hint": "Set \"fallback\": \"auto\" to send numbered text instead, or send text.",
    "doc_url": "https://api.flow.engineer/docs/errors/unsupported_content",
    "param": "content.type"
  }
}

{
  "error": {
    "type": "new_contact_limit",
    "message": "This sender has started its 15 new conversations for today.",
    "hint": "Retry after 3600 seconds; replies into existing conversations still go.",
    "doc_url": "https://api.flow.engineer/docs/errors/new_contact_limit",
    "retry_after": 3600,
    "sender": "snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T"
  }
}

{
  "error": {
    "type": "invalid_request",
    "message": "<string>",
    "hint": "Send a template instead: POST /v1/messages with content.type=template.",
    "doc_url": "https://api.flow.engineer/docs/errors/outside_window",
    "param": "<string>",
    "retry_after": 1,
    "conversation": "conv_01JB8ZC3K5M7P9R1T3V5X7Z9B1",
    "sender": "snd_01JB8Z4Q3V6W0R2N7C5H1M9K4T",
    "channel_code": "<string>",
    "request_id": "<string>"
  }
}