# Arsen MCP

> Connect an assistant to read Simulation and Training data in the Arsen Organizations you can access.

MCP endpoint: https://api.arsen.co/mcp

This page covers connection setup and troubleshooting. Connected clients discover available tools through MCP `tools/list`. Tool descriptions and schemas are supplied by the server, including supported inputs, defaults, output definitions and usage limits. Use those live definitions when calling tools.

## Connect Arsen to your assistant

Arsen uses remote HTTP OAuth with browser sign-in and explicit Arsen consent. Set up the MCP connection in your client; it is independent of the model you use. Never paste credentials or authorization callbacks into chat.

Personal MCP API keys issued through Arsen also work as bearer credentials and grant both `mcp:read` and `mcp:write` by default. OAuth connections retain their explicitly approved scopes. Campaign launch still requires the eligible demo Organization and current campaign-create permission.

### Hosted assistants

- **Claude.ai / Claude Desktop:** add a custom remote MCP connection using the endpoint above, complete browser sign-in, and enable the connection for your conversation. [Claude setup](https://support.claude.com/en/articles/11175166-get-started-with-custom-connectors-using-remote-mcp).
- **ChatGPT:** add a custom MCP connection using the endpoint above, choose OAuth, and complete browser sign-in. Enable the connection for your conversation. [ChatGPT setup](https://developers.openai.com/api/docs/guides/custom-mcp-server).

Your account or workspace must allow custom MCP connections. Setup happens in the assistant’s connector settings; a command in its code sandbox cannot configure your account.

### Local coding agents

Use the instructions for the client you are running. Reuse a matching Arsen connection and preserve other settings; ask before replacing an existing connection.

| Client | Setup |
| --- | --- |
| [Claude Code](https://code.claude.com/docs/en/mcp) | Run `claude mcp add --transport http --scope user arsen 'https://api.arsen.co/mcp'`, then use `/mcp` to sign in. |
| [Codex CLI / IDE](https://learn.chatgpt.com/docs/extend/mcp?surface=cli) | Use the short configuration below, then sign in. |
| [Cursor](https://cursor.com/docs/mcp) | Add `"arsen": { "url": "https://api.arsen.co/mcp" }` under `mcpServers` in `~/.cursor/mcp.json`, then authenticate in MCP settings. |
| [VS Code / GitHub Copilot](https://code.visualstudio.com/docs/agent-customization/mcp-servers) | Run **MCP: Add Server**, choose HTTP, enter the endpoint above and name it arsen. Choose user configuration and complete sign-in. |
| [OpenCode](https://opencode.ai/docs/mcp-servers/) | Add `"arsen": { "type": "remote", "url": "https://api.arsen.co/mcp", "oauth": { "scope": "mcp:read mcp:write" } }` under `mcp` in your OpenCode configuration, then run `opencode mcp auth arsen`. |
| [Gemini CLI](https://geminicli.com/docs/tools/mcp-server/) | Run `gemini mcp add --transport http --scope user arsen 'https://api.arsen.co/mcp'`, then use `/mcp auth arsen` in Gemini. |

For Codex, add this entry to `~/.codex/config.toml` or `$CODEX_HOME/config.toml` if you use a custom home:

```toml
[mcp_servers.arsen]
url = "https://api.arsen.co/mcp"
scopes = ["mcp:read", "mcp:write"]
```

```sh
codex mcp login arsen --scopes mcp:read,mcp:write
```

Complete sign-in and consent in the browser. Reload the client’s MCP connections if the tools do not appear. For another MCP client, use the same endpoint with HTTP transport and OAuth; request `mcp:read mcp:write` if it asks for scopes.

### Sandboxed agents

If your runtime cannot configure MCP connections or reach the endpoint, use the host’s connector settings or complete setup on your own machine. A blocked network needs an administrator to allow the endpoint.

## Check the connection

After sign-in, refresh the client connection and confirm that MCP tool discovery succeeds. Use the discovered tool definitions to make an authorized read when checking data access. Signing in does not grant Organization membership; accessible data depends on your current Arsen permissions.

## Troubleshooting

- **No tools appear:** confirm the connection is enabled and that your account or workspace permits custom MCP connections. Refresh the connection after completing sign-in.
- **Sign-in expired:** authenticate again through the client and complete browser consent.
- **Organization unavailable:** check your Arsen membership or ask an administrator to grant access.
- **Consent denied or access disconnected:** reconnect only when the user chooses to restore access.
- **Tool call failed:** follow the returned error guidance. When contacting support, include the request ID from the failure.

Existing personal MCP JWT connections remain usable until revoked; switching to OAuth is optional.