### Answer To send a Slack message from your Retell AI agent, you have two main options: Custom Function or MCP. ## Option 1: Custom Function Create a custom function that calls the Slack API [(1) ]() : 1. In your agent's Functions section, click + Add and select Custom Function 2. Configure the function: - **Name**:

send_slack_message

- **Description**: Describe when to send Slack messages - **HTTP Method**: Select POST - **Endpoint URL**: Your Slack webhook URL or API endpoint 3. Set request headers with your Slack authentication token 4. Define parameters using JSON schema format for the message content 5. Optionally set response variables to extract values from Slack's API response The custom function will send a POST request to your specified Slack endpoint with the function name and parameters . ## Option 2: MCP (Model Context Protocol) If you have an MCP server that handles Slack integration [(2) ]() : 1. Click + Add MCP in your agent configuration 2. Connect to your MCP server endpoint 3. Set custom headers for authentication (optional) 4. Select the Slack-related MCP tool from available tools 5. Configure response variables to extract data 6. Update your agent prompt to specify when to invoke the MCP tool Both approaches let your agent send Slack messages during conversations. Custom Functions give you direct API control, while MCP provides a standardized integration layer.

​ To learn more, see the sources I considered: [[1] Custom Function](https://docs.retellai.com/build/conversation-flow/custom-function) [[2] MCP](https://docs.retellai.com/build/single-multi-prompt/mcp) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.