# Transfer and call, a new entrypoint for FA2
**URL:** https://forum.tezosagora.org/t/transfer-and-call-a-new-entrypoint-for-fa2/3144
**Category:** TZIP
**Created:** [May 20, 2021, 1:22pm UTC](https://forum.tezosagora.org/t/transfer-and-call-a-new-entrypoint-for-fa2/3144 "2021-05-20T13:22:59Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Jordan](https://forum.tezosagora.org/u/Jordan)
#### Post date: [May 20, 2021, 1:22pm UTC](https://forum.tezosagora.org/t/transfer-and-call-a-new-entrypoint-for-fa2/3144/1 "2021-05-20T13:22:59Z")
# Transfer and call
## Key points
- SmartPy team proposed as new TZIP inspired by [ERC677](https://github.com/ethereum/EIPs/issues/677) with a `transfer_and_call` entry-point.
- You can read the whole [here](https://gitlab.com/tzip/tzip/-/blob/b40b4ef8d966a610a6cd8515dcf6ade9739121b9/proposals/tzip-23/tzip-23.md).
- Here is the [merge request](https://gitlab.com/tzip/tzip/-/merge_requests/163).
- Here is a example of a scenario using it: [SmartPy](https://smartpy.io/ide?cid=QmeVo8dGqCgvTmt5NewZxCsZ5SS5PNSMLpCgLBBqMaHDAg&k=181eb256d440a3b9c9a7).
- We are waiting for your comments and suggestions.
## A new entry-point for FA2
TZIP-23 extends FA2 token specifications by introducing a multi-action
transfer entry point. The entry point adds a proxy mechanism to the standard
transfer behavior, allowing the source to send a request or notify the recipient
after a successful transfer.
This TZIP adds a new entry-point to FA2 token contracts,
`transfer_and_call` which can be called to transfer tokens to a contract and
send a follow up call. Once the tokens are transferred, the token contract calls
the receiving contract’s entry-point given in argument with the specified data.
The `transfer_and_call` is inspired by [ERC677](https://github.com/ethereum/EIPs/issues/677)).
## Motivation
Currently, the FA2 transfer standard doesn’t offer any mechanism to allow the
sender to notify the recipient of a transaction. This mechanism is necessary to
improve the interoperability between contracts. As a result, it will turn the
communication more decentralized by removing off-chain dependencies.
## Interface Specification
Token contract implementing this TZIP standard MUST implement the given entrypoint: [`transfer_and_call`](#transfer_and_call)
### `transfer_and_call`
```michelson
(list %transfer_and_call
(pair
(address %from_)
(list %txs
(pair
(address %to_)
(address %callback)
(bytes %data)
(nat %token_id)
(nat %amount)
)
)
)
)
```
The entrypoint SHALL perform and only perform the following 3 actions:
1. Regular transfer
2. Callback verification
3. Callback
The entrypoint SHOULD NOT perform any extra logic and SHOULD NOT call any other
contract or rely on any other instruction that can fail because of a third party.
### Regular transfer
The transfer part of the `transfer_and_call` MUST work **exactly** like a call to
the `transfer` entrypoint would have do (see FA2#transfer).
### Callback verification
The contract MUST verify the validity each `%callback`.
The `%callback` address is in the form: `prefix` `hash` `suffix` where `suffix`
is in the form `%entrypoint`
The `%to_` address is in the form: `prefix` `hash` (even if nothing prevents
user sending an entrypoint).
The transaction MUST FAILWITH `"FA2_CALLBACK_AND_RECEIVER_DIFFERS"` if
`%callback` and `%to_` differ by more than the `suffix`.
### Callback
The contract MUST return a list of transfer operation for each `%callback` in
the **same order** that the transfer are performed without deduplicating or
aggregating them with the following type argument:
```auto
(pair
(address %sender)
(bytes %data)
(nat %token_id)
(nat %amount)
)
)
```
* * *
Thank you for reading.
We are waiting for your comments and suggestions!
---
### Author:  [@mpsp](https://forum.tezosagora.org/u/mpsp)
#### Post date: [May 20, 2021, 5:52pm UTC](https://forum.tezosagora.org/t/transfer-and-call-a-new-entrypoint-for-fa2/3144/2 "2021-05-20T17:52:59Z")
> [@Jordan](#):
>
> tierce entity
Might want to adjust the wording here.
---
### Author:  [@Jordan](https://forum.tezosagora.org/u/Jordan)
#### Post date: [May 20, 2021, 6:01pm UTC](https://forum.tezosagora.org/t/transfer-and-call-a-new-entrypoint-for-fa2/3144/3 "2021-05-20T18:01:45Z")
Thank you.
Changed to `third party`
---
### Author:  [@arrijabba](https://forum.tezosagora.org/u/arrijabba)
#### Post date: [May 25, 2021, 5:06pm UTC](https://forum.tezosagora.org/t/transfer-and-call-a-new-entrypoint-for-fa2/3144/4 "2021-05-25T17:06:43Z")
i get it but is there any way to keep this entrypoint optional? message passing in Tezos is still pretty unsafe even with DFS. So like I’m sure there would be folks who want to use this, so i support the TZIP generally. but if I want to make a complex contract and embed an FA2 token inside, I don’t want to be forced into implementing this endpoint to get my little “FA2” badge.
---
### Author:  [@Jordan](https://forum.tezosagora.org/u/Jordan)
#### Post date: [October 21, 2021, 12:15pm UTC](https://forum.tezosagora.org/t/transfer-and-call-a-new-entrypoint-for-fa2/3144/5 "2021-10-21T12:15:53Z")
I updated the proposal.
Now we can specify a callback address that is totally different from the receiving address. The receiving address is now passed in the callback args.
It removed the need of `same_underlying_address` verification which was not well standardize in Michelson.
**Callback is now**
```auto
(pair
(nat %amount)
(bytes %data)
(address %receiver)
(address %sender)
(nat %token_id)
)
```