Slack: Provide custom unfurl behavior for user-posted UR Ls

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Operation slack.chat_unfurl

Provider route: POST /chat.unfurl. Alter supplies the connection’s credentials and routing.

Call through Alter

Install @alter-ai/sdk @alter-ai/slack with npm, or alter-sdk-slack with pip. Supply your connected customer’s grant ID and the arguments described below.

import { App } from "@alter-ai/sdk";
import { SlackIntegration } from "@alter-ai/slack";

async function execute(input: Parameters<SlackIntegration["chat"]["unfurl"]>[0]) {
  const app = new App({ apiKey: process.env.ALTER_API_KEY! });
  try {
    const provider = new SlackIntegration(app, { grantId: process.env.PROVIDER_GRANT_ID! });
    const call = await provider.chat.unfurl(input);
    const result = await call.wait();
    return result.bodyJson();
  } finally {
    await app.close();
  }
}

import os
from alter_sdk import App
from alter_sdk_slack import SlackIntegration

async def execute(arguments):
    async with App(api_key=os.environ["ALTER_API_KEY"]) as app:
        provider = SlackIntegration(app, {"grant_id": os.environ["PROVIDER_GRANT_ID"]})
        call = await provider.chat.unfurl(arguments)
        result = await call.wait()
        return result.body_json()

Input

Field	Type	Presence	Description and constraints
$	object	Root	Additional keys: not allowed
body	object	Optional
body.channel	string	Optional	Channel ID of the message. Both `channel` and `ts` must be provided together, or `unfurl_id` and `source` must be provided together. Required for public channels.
body.source	string	Optional	The source of the link to unfurl. The source may either be `composer`, when the link is inside the message composer, or `conversations_history`, when the link has been posted to a conversation.
body.ts	string	Optional	Timestamp of the message to add unfurl behavior to. Required for public channels.
body.unfurl_id	string	Optional	The ID of the link to unfurl. Both `unfurl_id` and `source` must be provided together, or `channel` and `ts` must be provided together.
body.unfurls	string	Optional	URL-encoded JSON map with keys set to URLs featured in the message, pointing to their unfurl blocks or message attachments. Required for public channels.
body.user_auth_blocks	string	Optional	Provide a JSON based array of structured blocks presented as URL-encoded string to send as an ephemeral message to the user as invitation to authenticate further and enable full unfurling behavior
body.user_auth_message	string	Optional	Provide a simply-formatted string to send as an ephemeral message to the user as invitation to authenticate further and enable full unfurling behavior. Provides two buttons, `Not now` or `Never ask me again`.
body.user_auth_required	boolean	Optional	Set to `true` or `1` to indicate the user must install your Slack app to trigger unfurls for this domain
body.user_auth_url	string	Optional	Send users to this custom URL where they will complete authentication in your app to fully trigger unfurling. Value should be properly URL-encoded.

Response

Response media type: application/json. The table describes the pinned successful response. Referenced models link to their complete fields.

Field	Type	Presence	Description and constraints
$	object	Root	Schema for successful response from chat.unfurl method
ok	boolean	Required within parent	Must equal: true

Policy, approvals and errors

SDK function policy ID: slack.chat_unfurl. Catalog operation: chat_unfurl. Rules can name either ID; function rules distinguish managed calls and conservatively cover raw calls sharing the route. Existing grant permissions and policy rules apply. wait() returns an immediate result or waits for a required approval; it never approves the request itself. Persist the approval ID to resume after a restart.

Provider errors retain their response; JSON decoding raises ProviderAPIError for provider failures. ManagedOperationError identifies contract/input/retention errors. See error handling and provider-specific behavior. Sensitive input may be refused before approval storage. A decoding error never resubmits a write.

Required provider scopes: ["links:write"]

Official provider source