# DDL issues

You may find that some [DDL operations](https://tray.ai/documentation/developer/getting-started/calling-connectors/ddl-operations/) (identified as 'lookup' in the input schema) may be missing parameters which affect their functionality.

For example:

* They may not have any **pagination parameters**
* They may miss **filtering options** for returned lists of data

A case in point is that the Slack `send_message` operation has a `list_users_and_conversations_ddl` to allow the user to select the channel they wish to send the message to.

However if you have more than 1000 channels (the max returned by the Slack API) then you will be unable to paginate with the DDL operation.

In this case, it is recommended that you make use of the [Ops Explorer dev tool](https://tray.ai/documentation/developer/developer-tools/operations-explorer) to find a non-DDL version of the operation.

In this case you can make use of the `list_conversations` operation, which accepts the `limit` and `cursor` pagination parameters:

```json
{
  "operation": "list_conversations",
  "authId": "af75fxxx-xxx-xxx-xxx8c494c5",
  "input": {
    "limit": 10,
    "cursor": "dGVhbTpDRTZEN0s2UTM="
  },
  "returnOutputSchema": false
}
```

After using this to allow a user to select the channel you can pass their choice as a direct input for `channel` in the `send_message` operation:

```json
{
  "operation": "send_message",
  "authId": "af75fxxx-xxx-xxx-xxx8c494c5",
  "input": {
    "channel": "{{channel}}",
    "text": "more please!",
    "as_user": true
  },
  "returnOutputSchema": false
}
```