Slack api conversations.history returns error: not_in_channel

I'm starting out with the Slack API and trying to just get a list of messages.

Here are my steps:

1. Created a Slack app and gave it channels:read and channels:history scope (also re-installed it)
2. Queried the list of channels with conversations.list (this worked fine)
3. From the output of conversations.list, I found a channel that I use and copied the id
4. Used the conversations.history api with the channelid from step 3

Result:

{ "ok": false, "error": "not_in_channel" }

I'm not at all sure what is happening here. I definitely have messages in the channel, and the documentation page for that api does not say anything about this "not_in_channel" error code.

What am I doing wrong?

After a long time of investigations (~2 hours), I found an easy approach. For Caleb's answer, I didn't understand how to invite a Bot to the channel. Hence, I am posting this answer.

Go to your Slack Channel and type the following as a message.

/invite @BOT_NAME

Eg: If your Bot name is SRE Incident Manager the command would be as follows.

/invite @sre_incident_manager

As soon as you start typing @, Slack will automatically suggest. So it becomes easy. For this, the Bot needs to be added to your Slack Workspace.

PS: Original answer.

This error arises when you are using the bot oauth token and the bot is not invited to the channel. To solve this you need to

• Invite the bot(slack app) to join the channel.
• Use the OAuth Access Token instead

To add Bot to your channel you need to write /invite @Bot_name in the slack channel

The error not_in_channel has the exact meaning, your custom Slack app should be added to the channel.

Exact solution 1

To resolve the error, in the Web Slack interface:

• Open channel settings
• Click on the Integrations tab
• Click Add apps and find your custom app.

Slack app might have different interface, see Iryna Vernik's answer.

Alternative solution 2

Give access to the bot to all channels by adding workspace wide scope, for example, chat:write.public. Depends on your needs and security requirements.

Alternative solution 3

To access the channel chat from API specify Incoming webhook. Slack will generate a unique URL with the token per each channel. Only convenient for a few channels.