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How to integrate Cartesia MCP with Hermes

Connect Hermes to Cartesia MCP. Convert text to speech with cartesia, transcribe a cartesia audio recording, and more using natural language, with authentication handled for you.

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Cartesia is a real-time voice AI platform for text-to-speech, speech-to-text, and managed voice agents. It helps developers build fast, natural voice experiences with powerful audio APIs.

10 Tools

Introduction

Hermes is a 24/7 autonomous agent that lives on your computer or server — it remembers what it learns and evolves as your usage grows.

This guide explains the easiest and most robust way to connect your Cartesia account to Hermes. You can do this through either Composio Connect CLI or Composio Connect MCP. For personal use we recommend the CLI, but you won't go wrong with MCP either.

Also integrate Cartesia with

ChatGPTClaude CoworkAtomic Agent

What is Composio Connect?

Composio Connect is a consumer offering that lets anyone plug 1,500+ applications directly into their agent harness — including Hermes. It can:

  • Search and load tools from relevant toolkits on-demand, reducing context usage.
  • Chain multiple tools to accomplish complex workflows via a remote workbench, without excessive back-and-forth with the LLM.
  • Manage app authentication end-to-end with zero manual overhead.

Integrating Cartesia with Hermes

Using Composio Connect CLI

1. Install the Composio CLI

Run the install script directly, or paste https://composio.dev/hermes into your Hermes chat box to have it installed for you.

bash
curl -fsSL https://composio.dev/install | bash
Hermes authenticating with Composio

2. Authenticate

Once the CLI is installed, ask Hermes to authenticate with Composio.

3. Connect to Cartesia

Ask your agent to connect to Cartesia, or simply request any Cartesia-related task. Hermes will prompt you to authenticate and authorize access.

4. Done. You're all set with a new Cartesia connection.

Using Composio Connect MCP

1. Get your MCP URL and API Key

Go to dashboard.composio.dev and copy your Connect MCP URL and API key.

Copy MCP URL and API key from Composio dashboard

2. Open the Hermes config file

bash
nano ~/.hermes/config.yaml

3. Add the Composio Connect MCP server

bash
mcp_servers:
  composio:
    url: "https://connect.composio.dev/mcp"
    headers:
      x-consumer-api-key: "YOUR_COMPOSIO_API_KEY"
    connect_timeout: 60
    timeout: 180

Save with Ctrl + O, Enter, then exit with Ctrl + X.

4. Restart your Hermes agent

Once restarted, ask your agent to connect to Cartesia or request any Cartesia-related task. It will prompt you to authenticate and authorize access.

5. Done!

What is the Cartesia MCP server, and what's possible with it?

The Cartesia MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Cartesia account. It provides structured and secure access to voice, speech synthesis, pronunciation dictionary, accent, and managed agent model capabilities, so your agent can generate audio from text, find suitable voices, check supported accents, manage pronunciation dictionaries, and review available agent models on your behalf.

  • Text-to-speech generation: Have your agent turn a complete transcript into a downloadable audio file using a selected Cartesia voice.
  • Voice discovery: Let the agent search Cartesia voices and retrieve synthesis details to help choose the right voice for an audio project.
  • Accent exploration: Direct your agent to list supported accents and filter them by language, locale, or voice localization support.
  • Pronunciation dictionary management: Instruct your agent to create, review, update, list, or delete reusable pronunciation dictionaries for more consistent speech generation.
  • Managed agent model selection: Have your agent review available Cartesia managed agent models, including provider, latency, and pricing details.

Way Forward

With Cartesia connected, Hermes can now act on your behalf whenever it detects a relevant task or you ask it to.

From here, you can extend Hermes further:

  • Connect more apps: Calendar, Slack, Notion, Linear, and hundreds of others are available through the same Composio Connect setup. Each new integration compounds what Hermes can do for you.
  • Build workflows across tools: Once multiple apps are connected, Hermes can chain actions together — turn an email into a calendar invite, a Slack message into a Linear ticket, or a meeting note into a follow-up draft.
  • Let it learn your patterns: The more you use Hermes, the better it gets at anticipating how you'd handle recurring tasks. Give it feedback on drafts and decisions, and it will adapt.

If you run into trouble or want to share what you've built, join the community or check out the Docs for deeper configuration options.

TOOLS

Supported Tools

Every Cartesia action and event your agent gets out of the box.

Create Pronunciation Dictionary

Create a reusable pronunciation dictionary for text-to-speech generation.

Delete Pronunciation Dictionary

Permanently delete one pronunciation dictionary by ID.

Get Pronunciation Dictionary

Return one pronunciation dictionary and its complete text-to-pronunciation mappings.

Get Voice

Return synthesis-relevant details for one Cartesia voice by ID.

List Accents

List supported accents, optionally filtered by language, locale, or voice-localization support.

List Agent Models

List language models available to Cartesia Managed Agents, including provider, latency, and pricing metadata.

List Pronunciation Dictionaries

Return one page of pronunciation dictionaries available to the connected account.

List Voices

Search and filter Cartesia voices, returning one page of voice IDs and synthesis-relevant metadata.

Synthesize Speech

Generate a downloadable audio file from one complete transcript using a selected Cartesia voice; usage is billed by transcript length.

Update Pronunciation Dictionary

Update a pronunciation dictionary and replace its mappings with the complete supplied item set.

FRAMEWORKS

How to build Cartesia MCP Agent with another framework

ChatGPT logo

ChatGPT

Use Cartesia MCP with ChatGPT

Claude Cowork logo

Claude Cowork

Use Cartesia MCP with Claude Cowork

Atomic Agent logo

Atomic Agent

Use Cartesia MCP with Atomic Agent

FAQ

Frequently asked questions

With a standalone Cartesia MCP server, the agents and LLMs can only access a fixed set of Cartesia tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Cartesia and many other apps based on the task at hand, all through a single MCP endpoint.

Yes, you can. Hermes fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Cartesia tools.

Yes, absolutely. You can configure which Cartesia scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Cartesia data and credentials are handled as safely as possible.

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