How to integrate Nango MCP with DeepSeek Harness

Connect DeepSeek Harness to Nango MCP. List all connected crm accounts, trigger manual sync with salesforce provider, and more using natural language, with authentication handled for you.

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Nango

Api Key

Nango is a unified API platform that connects to 250+ SaaS apps across CRM, HR, and accounting. Streamline integrations with one API and simplify data sync across your business tools.

24 Tools

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Introduction

DeepSeek Harness (dsh) is an open-source agent runtime from DeepSeek AI, and every part of it is a plugin, so you can swap out the model adapter, the tool registry, or the agent loop. It runs on the Cordis framework and comes with a local Web UI, a headless CLI runner, and a Python SDK. You can point it at DeepSeek V4-Pro and V4-Flash, or at Anthropic, OpenAI, and other OpenAI-compatible providers. It is MIT licensed and still in developer preview.

This guide shows how to connect your Nango account to DeepSeek Harness, and you can do it with either the Composio Connect CLI or the Composio Connect MCP. The dsh-base bundle gives shell execution as a first-class tool, so the CLI is the easiest path for personal use. It is quick to set up and needs no server config, and the MCP path works well too, since the harness comes with a built-in MCP client.

What is Composio Connect?

Composio Connect lets anyone plug 1,000+ applications directly into their agent harness, including DeepSeek Harness, through a single hosted MCP endpoint. Each task runs as a session, a scoped runtime that ties together the user, the available toolkits, authentication, and execution state. It can:

Discover and load tools on-demand. A small set of meta tools lets the agent search for the right tool at runtime, so you never load hundreds of tool definitions into context.
Chain tools in a sandboxed remote workbench. Multi-step workflows run server-side, passing outputs between tools and working with files in the session's sandbox, so long chains finish without a lot of back-and-forth with the LLM.
Manage authentication end-to-end. Managed OAuth, per-user connected accounts, and account isolation are all handled for you, so you never wire up auth yourself.

Connect Nango to DeepSeek Harness with Composio

Prerequisites: Install DeepSeek Harness

DeepSeek Harness needs Node.js (20 or 22) and pnpm. Build it from source. This is also what the MCP path in Option 2 requires, since the built-in MCP client resolves its dependencies from the checkout:

bash

git clone https://github.com/deepseek-ai/deepseek-harness.git
cd deepseek-harness
pnpm install
pnpm run build
pnpm dsh web

The Web UI listens on http://127.0.0.1:3080 by default. Open that address to confirm it is up.

Then configure your model route. In the Web UI, open Settings → Models: the built-in DeepSeek card accepts a DeepSeek API key, and the same page supports Anthropic, OpenAI, and custom OpenAI-compatible endpoints. Full first-run details are in the DeepSeek Harness docs.

Option 1: Composio CLI (recommended)

DeepSeek Harness runs shell commands as a first-class tool through its dsh-base bundle, so the Composio Universal CLI fits well. There is no MCP server to configure, and multi-step tool chaining is reliable. Install and authenticate:

bash

# Install the Composio CLI
curl -fsSL https://composio.dev/install | bash

# Log in to Composio
composio login

Connect to Nango

Ask DeepSeek Harness to connect to Nango, or just request any Nango-related task. Under the hood the agent calls Composio commands like any other shell tool:

bash

composio search "what can I do with Nango?"
composio link nango

On the first Nango call, composio link nango opens an OAuth prompt so you can authorize access. After that, every Nango command works with your stored credentials automatically, so you just talk to the agent and it will search, execute, and chain Nango tools as needed.

Option 2: Composio MCP

DeepSeek Harness bridges MCP through its built-in @deepseek-ai/dsh-mcp-client plugin. You register one server as a plugin row, and its tools appear under server-qualified names (mcp__<serverName>__<rawName>), the same shape Claude Code and Codex use.

MCP requires the source build. The built-in client depends on the harness's own internal packages (cordis, dsh-llm, dsh-tools, dsh-invariants, dsh-subprocess), which resolve from the git checkout you built in the prerequisites. Run everything below from that checkout with pnpm dsh. For a route that avoids editing config files, see the community plugin at the end of this section.

Auth note: The built-in client passes static headers only and has no OAuth flow, so authenticate to Composio Connect with the x-consumer-api-key header. For Composio's OAuth flow, use the community plugin below.

1. Register the Composio server

The web profile's user patch layer is $DSH_HOME/profiles/web/cordis.patch.yml ($DSH_HOME defaults to ~/.dsh). This is a patch file, so a new plugin goes under an insert: entry. A bare - id: row instead targets an existing entry and fails to boot with patch: entry "…" not found. Add:

bash

- insert:
    - id: mcp-composio
      name: '@deepseek-ai/dsh-mcp-client'
      config:
        serverName: composio
        transport: streamable-http
        url: https://connect.composio.dev/mcp
        headers:
          x-consumer-api-key: !!js process.env.COMPOSIO_API_KEY

2. Set the API key and launch

The header value must resolve to a string at load time. Export your Composio consumer API key (ck_...), which is on the Connect → Settings → Sessions page of the Composio dashboard, in the shell you launch from. If it is unset, process.env.COMPOSIO_API_KEY is undefined and the config fails validation:

bash

export COMPOSIO_API_KEY=ck_your_key
pnpm dsh web

3. Done!

Open http://127.0.0.1:3080 and start a session on Standard or Code mode. (Minimal mode exposes only bash and str_replace_editor, so it hides MCP tools.) Composio's tools register as mcp__composio__*. Ask DeepSeek Harness to connect to Nango or request any Nango-related task, and Composio authorizes Nango on demand on the first call.

The dsh-mcp-client config schema (transport, serverName, url, headers, plus reconnect.* and toolCallTimeoutMs) is the current developer-preview interface and may change between releases.

Alternative: OAuth via the community plugin

To use Composio Connect's OAuth flow instead of a static key, or to skip editing cordis.patch.yml by hand, use the community dsh-mcp-manager plugin. It installs as a self-contained external plugin, ships a bundle patch so it auto-mounts, and adds a Settings → MCP page plus OAuth (authorization code + PKCE, RFC 7591 dynamic client registration, and refresh-token rotation). It needs the web profile and Node.js ^22.19 or >=24, with pnpm on your PATH.

Install it from your source checkout, then restart pnpm dsh web and refresh:

bash

pnpm dsh plugin --profile web add github:hyqhyq3/dsh-mcp-manager

Open Settings → MCP → ＋ Add MCP server, choose HTTP, set the name to composio, the URL to https://connect.composio.dev/mcp, and the auth mode to OAuth. Click Authenticate, and Composio's login and consent screen opens in the browser, then redirects back and registers the tools as mcp__composio__*. The row should read connected (N tools).

The plugin catches the OAuth code on a loopback redirect (http://127.0.0.1:<port>/mcp-manager/callback/<id>), so Composio's OAuth provider must allow that loopback URL. Server configs and tokens persist at ~/.dsh/mcp-manager.json, so treat that file as a secret. Being a community plugin on a preview harness, its commands may change, so check the plugin repo if a step drifts.

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

The Nango MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Nango account. It provides structured and secure access to your integrations, so your agent can perform actions like triggering syncs, managing connections, listing providers, and executing workflow actions across 250+ external APIs on your behalf.

Connection management and discovery: Effortlessly list all your existing Nango connections, view metadata, or retrieve connection information without exposing sensitive credentials.
Provider information and browsing: Ask your agent to list all available providers or fetch detailed configuration info for a specific provider, making it easy to discover and set up new integrations.
Triggering workflow actions: Direct your agent to execute custom workflow actions by specifying the connection, provider, and action identifiers—unlocking advanced automation across connected platforms.
Manual sync initiation: Have your agent trigger sync processes for any established connection, ensuring your data stays up-to-date across all integrated services.
Script configuration retrieval: Let your agent fetch Nango scripts configuration and triggers, enabling more tailored and automated integration flows.

Way Forward

With Nango connected, DeepSeek Harness can now act on your behalf whenever you ask it to.

From here, you can extend the harness further:

Connect more apps: Calendar, Slack, Notion, Linear, and hundreds of others are available through the same Composio Connect setup, and each new integration adds to what your agent can do for you.
Build workflows across tools: Once multiple apps are connected, DeepSeek Harness can chain actions together, so it can turn an email into a calendar invite, a Slack message into a Linear ticket, or a meeting note into a follow-up draft.
Use the plugin system: Wrap common Nango flows as dsh plugins or prompt templates so recurring tasks become one-line commands, and bundle your most-used Nango tools into a named profile you can boot on demand.

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

TOOLS

Supported Tools

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

Trigger Nango Action

Trigger a Nango action to execute a workflow or operation.

Add Connection

Tool to add a connection with existing credentials to Nango.

List Connections

List all Nango connections without credentials.

Create Connect Session

Tool to create a new connect session with a 30-minute lifespan for enabling connection creation via Connect UI.

Create Integration

Tool to create a new integration in Nango.

Delete Connection

Tool to delete a specific Nango connection.

Delete Integration

Tool to delete a specific integration by its unique key.

Edit Connection

Tool to edit a connection's tags and metadata.

Get Connection with Credentials

Retrieve a specific connection with its credentials.

Get Environment Variables

Tool to retrieve environment variables from the Nango dashboard.

Get Integration

Retrieve detailed configuration for a specific Nango integration by its unique key.

Proxy GET Request

Tool to make a GET request with Nango's Proxy to forward requests to external APIs while managing authentication.

Get Sync Status

Tool to get the status of specified sync(s) for a connection or all connections.

List Connections

Tool to list all connections without credentials.

List Integrations

Tool to retrieve a list of all configured integrations.

Get Provider Details

Retrieve detailed configuration for a specific Nango provider by its unique key.

List Providers

Tool to retrieve a list of all available providers.

Proxy PUT Request

Tool to make a PUT request with the Nango Proxy to forward requests to external APIs while managing authentication.

Reconnect Session

Create a new connect session to reconnect to a specific integration.

Get Integration Functions Configuration

Retrieve all integration functions configuration from Nango.

Set Connection Metadata

Tool to set custom metadata for one or more Nango connections.

Trigger Sync

Tool to trigger sync process(es) manually.

Update Connection Metadata

Tool to edit custom metadata for one or multiple connections.

Update Integration

Tool to update an existing integration's configuration.

FRAMEWORKS

How to build Nango MCP Agent with another framework

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FAQ

Frequently asked questions

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

Yes, you can. DeepSeek Harness 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 Nango tools.

Yes, absolutely. You can configure which Nango 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 Nango data and credentials are handled as safely as possible.

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How to integrate Nango MCP with DeepSeek Harness

Connect Nango without auth hassles

Introduction

Also integrate Nango with

What is Composio Connect?

Connect Nango to DeepSeek Harness with Composio

Prerequisites: Install DeepSeek Harness

Option 1: Composio CLI (recommended)

Connect to Nango

Option 2: Composio MCP

1. Register the Composio server

2. Set the API key and launch

3. Done!

Alternative: OAuth via the community plugin

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

Way Forward

Supported Tools

How to build Nango MCP Agent with another framework

ChatGPT Work

Antigravity

OpenAI Agents SDK

Claude Agent SDK

Claude Code

Claude Cowork

Codex

Grok Build

Cursor

VS Code

OpenCode

OpenClaw

Hermes

Pi

Google ADK

LangChain

Vercel AI SDK

Mastra AI

LlamaIndex

CrewAI

Pydantic AI

AutoGen

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Supabase

Codeinterpreter

GitHub

1password

Frequently asked questions

What are the differences in Tool Router MCP and Nango MCP?+

Can I use Tool Router MCP with DeepSeek Harness?+

Can I manage the permissions and scopes for Nango while using Tool Router?+

How safe is my data with Composio Tool Router?+

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