Introduction - Rasa Documentation

Mantle is the orchestrator at the heart of the Rasa Platform. Once you have described what your agent should do through Skills, Mantle runs the conversation: choosing which skill is active, handing off between them gracefully, calling your tools, and keeping track of everything it has learned along the way.

Why Mantle

Mantle is built around progressive control: natural language instructions where that’s enough, and deterministic guarantees when there’s no room for ambiguity. Every skill starts as simple instructions. When you need more control, you add framework-enforced guarantees (a required value, a confirmation step, exact wording, a strict sequence) one lever at a time, without rewriting the skill.

Start simple

Write a skill as natural-language instructions. The LLM handles the conversation.

Add control

Add guarantees only where the business needs them. Nothing else changes.

Ship reliably

Get deterministic behavior on the steps that matter, at any scale.

What a skill looks like

The simplest skill is a single file, holding instructions in the Anthropic skill.md format:

skills/card_replace/skill.md

---
name: Card Replace
description: Replace a credit card -- lost, stolen, damaged, or not received
---

Help the customer replace a credit card.

Check whether their account is eligible for replacement. If they have
multiple cards, ask which one. Ask why they need a replacement -- the valid
reasons are lost, stolen, damaged, or not received.

Once everything is gathered, ask their shipping preference, confirm the
order, and process the replacement.

That’s a working skill. As it grows, the same folder holds everything the skill needs: instructions, tools, memory, references, and responses.

One skill, chat and voice

The same skill runs on chat and voice conversations. On voice, Mantle has the agent speak in short sentences without formatting, say numbers and dates aloud, fill the pause while a tool runs, and stop when the caller talks over it. You write the skill once, and tune how it sounds where that matters. Speech runs on the provider you choose, such as Deepgram, Azure, Cartesia, or Rime. See Voice agents for what Mantle handles on a call, or Build a voice agent to take this skill to the phone.

Next steps

Getting Started

Install Mantle, build your first agent with the Rasa Copilot, and talk to it by chat or voice.

Skills

The core building block: what a skill is and what goes in it.

Progressive Control

The control spectrum, one lever at a time.

Voice agents

Run the same skills in a voice conversation.

Reference

File formats, the tools contract, and runtime internals.

Building with CALM

Open the CALM docs for flows, Rasa Pro, and Studio 1.x.

​Why Mantle