### Answer Based on the available sources, I don't have specific documentation about MCP (Model Context Protocol) tool payloads in Retell AI. However, for standard Custom Functions/Tools, there's relevant context from a Discord discussion: when using custom tools, the webhook can receive different "streams" - transcript-only events (just text) versus structured events (including tool calls with

name

+

args

) . [(1) ]() A community member noted that if your webhook is only subscribed to the transcript stream, you won't see tool payloads. The tool must also be properly registered in the agent's configuration for the JSON payload to be emitted. For the LLM WebSocket, when

transcript_with_tool_calls

is set to

true

in the config event, Retell populates the

transcript_with_tool_calls

field in update events, which contains the transcript weaved with tool call invocations and results. [(2) ]() I don't have explicit documentation on whether MCP tools specifically include transcript in their payload. You may want to check the MCP-specific documentation or reach out for clarification: - [Contact Sales]() - [GitHub]() Would you like me to provide a general answer based on my knowledge instead?

​ To learn more, see the sources I considered: [[1] Discord message from @majestic_fawn_50137 on 2025-09-17](https://discord.com/channels/1186424376300679209/1186462578310910112/1417915583340478515) [[2] LLM WebSocket](https://docs.retellai.com/api-references/llm-websocket) ​

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