Heimdall
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Heimdall is a lightweight service to manage local [MCP Servers](https://modelcontextprotocol.io/introduction) and can be installed with a single `npx` command. Specific MCP server tools can be authorized for your MCP clients, and the same config is accessible to all MCP clients on your device.
Installation
<strong>NOTE:</strong> We strongly recommend backing up your MCP server config before installation to protect against unexpected loss of credentials.
The setup script performs a few key actions:
- Moves the `mcpServers` config JSON from the path you specify to `~/.heimdall/config.json`
- Inserts a single config for `heimdall` in place of the previous `mcpServers` config path
- Initializes the controls at `~/.heimdall/controls.json` to authorize all methods on all current servers
See [Configuration](#configuration) for steps to modify `~/.heimdall/controls.json` to limit the authorized tools for a given server, and add new servers to `~/.heimdall/config.json`.
Via NPX (Recommended)
- Run setup script (generates an empty config if no path is given):
Via Local Instance
- Download the package:
- Install and build dependencies:
- Run setup script (generates an empty config if no path is given):
Configuration
Edit Server List
To add or update available servers, simply update the configuration at `~/.heimdall/config.json` as your regular `mcpServers` config JSON. Note that you will not see tools for new servers through Heimdall unless you also add the server and authorized tools to `~/.heimdall/controls.json`.
Edit Authorized Tools
To add authorized tools to a new or existing server, add them as needed to `~/.heimdall/controls.json` and Heimdall will update its internal config after a few seconds. If your MCP client supports dynamic tool list caching, you should see it update the authorized tools automatically. Other clients (ex. Claude Desktop) may require a restart to see the new tools.
This is the schema for `~/.heimdall/controls.json`:
Multiple MCP Clients
If you run multiple MCP clients on your device, you can set the following `config.json` for each new client to enable the same authorized tools across all of them (assuming Heimdall has already been set up on the device):
Troubleshooting
Available Tools
Some MCP Clients have limits on the number of tools available to agents at a given time. For example, Cursor only supports up to 40 tools across all servers, so the sum of `authorizedTools` in `controls.json` cannot exceed this number.
Logging
For logs on running instances, go to `~/.heimdall/logs`. Logs for each MCP client's instance of Heimdall and child servers are stored in separate directories identified by random UUIDs.
Orphaned Child Processes
If your MCP client shut downs unexpectedly or fails to send the correct `SIGTERM` signal to Heimdall before closing, there may be orphaned `node` (and `npm`) processes still running on your device afterward. For the time being these must be force stopped manually. If there are no other sensitive `node` processes running on your device, you can use this command as post-cleanup:
Contributing
Contributions are welcomed and encouraged. Contact austin@shinzolabs.com with any questions, comments or concerns.