Facebook sending permissions

Question

Just trying to understand how are permissions work. I send a message from page(I'm the admin) via API to myself:

POST https://graph.facebook.com/v2.8/_page_id_/
{
  "recipient": {
    "id": "_my_id_"
  },
  "message": {
    "text": "hello, world!"
  }
}

receive:

{
  "error": {
    "message": "(#230) Requires pages_messaging permission to manage the object",
    "type": "OAuthException",
    "code": 230,
    "fbtrace_id": "CofCWlt4GXP"
  }
}

Why does facebook reject me?

UPD1.

I do not understand the reason because of:

When your app is in Development Mode, the Send API will only work for admins, developers and testers of the app. After your app is approved and public, it will work for the general public.

Do I still need special permissions in development mode?

UPD2.

I got permission, but still not allowed to send messages via API:

{
  "error": {
   "message": "(#230) Requires pages_messaging permission to manage the object",
    "type": "OAuthException",
    "code": 230,
    "fbtrace_id": "GJRxafu1uNx"
  }
}

Answer 1

you need permissions for that. pages_messaging permission for that.

Check this page for more on how it works. Pages_messaging permission

This allows you to send and receive messages through a Facebook Page, but only within 24h hours after a user action. For post 24h messages see the next permission. Conversations through this API can only begin when someone indicates—through a Messenger plugin or directly messaging you—that they want to receive messages from you. Try getting a token with that permission from the graph explorer.

It should work after then.

https://developers.facebook.com/tools/explorer/

UPDATE:

Yes, you need specific permissions to be able to execute some of these actions. They're referring to the availability of the app there for use. When the app is in dev mode even the admin needs to get a token with the needed permissions to perform certain actions.