Custom MCP servers

When the app you need is not in the catalog, add your own connector: a packaged MCP server run in Harriet's sandbox, a remote HTTP MCP server, or tools generated from an existing REST API's OpenAPI spec.

Three ways to bring your own

Create custom MCP (npx / uvx). The link at the bottom of the Add connector dialog is for sandboxed servers not in the catalog. You provide the sandbox command and arguments — often the same npx or uvx command the package's README shows — and Harriet runs the package in an isolated environment. This is the path for published MCP packages from npm-style registries; it expects a runnable package command, not a Git clone of an arbitrary repository.

If the package lives on GitHub rather than PyPI, you can keep the usual uvx --from git+https://github.com/… command: Harriet fetches a snapshot instead of cloning with git. Tick Keep git+https sources only when the package needs a real git checkout. Use a GitHub token in the environment only when the repository is private.

Native MCP server. If you already run an MCP server over HTTPS JSON-RPC, register it with its MCP server URL. This fits vendor-hosted remote servers and internal MCP services you deploy yourself.

OpenAPI / Swagger. You do not always need to build an MCP server. When a vendor or internal system exposes a REST API with an OpenAPI or Swagger document, give Harriet the API base URL and the OpenAPI spec URL and it generates one MCP tool per operation. This is often the fastest way to make an existing internal API usable by skills.

Where servers are configured

Custom connectors are set up in Integration settings — the Connectors screen's own description points there: "Configure OAuth, server URLs, and tool permissions in Integration settings." Add MCP, in the ⋮ menu on the Connectors screen, opens the full setup flow.

The wizard steps through:

1. Basics. Display name and how the connector appears to admins.
2. Connection. Pick the type: OpenAPI / Swagger, native MCP server, or sandboxed (uvx / npx).
3. Authentication. No auth, basic auth, organization secrets, or per-user OAuth, depending on what the server supports. Organization secrets are configured once by IT and stored server-side; employees never receive them.
4. Access. Which teams may use the connector.

After saving, run Sync tools so Harriet discovers what the server offers, then decide which tools to enable — see Tool permissions. Once the connector exists, attach it to a skill and assign that skill like any other.

You can also ask your agent to do all of this from the vendor's documentation. See Set up connectors with your agent.

Build an integration with your agent

If your organization has Harriet code hosting enabled, people who can add connectors can ask a Harriet Desktop or cloud agent to build a new integration. The built-in Build integrations skill guides it through creating the source, publishing a version and configuring a sandboxed connector. You can keep the code on GitHub, or use Harriet's private repositories through your existing sign-in. On Harriet Desktop the agent needs Git on your computer, and asks you to install it if it is missing.

With Harriet hosting, the agent works with ordinary Git branches and commits. Publishing creates a fixed source archive; it does not automatically switch your live connector. The agent selects the published version using Bot Configurator, following your organization's existing review requirements. If you manage connectors, it creates the connector directly. Otherwise it submits the connector for review, and the connector stays inactive until an admin approves it. If Bot Configurator is not in your profile, the agent gives you the published values to add the connector under Connectors instead. To roll back, select an earlier published version. Harriet does not add a hosted build or test pipeline, and a published source archive does not freeze all of its dependencies.

Before calling the connector ready, the agent tests it in Harriet's sandbox and links it to a skill assigned to you. Harriet Desktop picks up the connector at its next sync, and the new tools appear when your session reloads.

On Connectors, open the ⋮ menu and choose Connector code to read source files, view recent commits and download published versions. The web interface is read-only; make changes through your Desktop or cloud workspace. Repositories currently support fast-forward updates and new branches, with no force pushes or remote branch deletion.

Enter credentials privately

When a connector needs an API token, an OAuth client secret or a credential file, the agent can request a private form in Harriet Desktop, including when Desktop is attached to a cloud workspace. Check the named connector and fields, enter the values or choose a credential file, then select Save credentials. The form sends them directly to encrypted connector storage. The agent receives only completion status; the values do not enter the conversation.

You can cancel a request, and unused requests expire after 30 minutes. If the private form is unavailable, use the connector's existing Integration settings form. Do not paste credentials into chat.

For OAuth, the agent sets up the connector's sign-in settings itself and tells you the redirect URI to register with the provider. It asks you only for the app's client ID and, through the private form, the client secret. When your own sign-in is needed, Harriet Desktop shows a Connect button in the chat. If you leave the chat during sign-in, return and select Continue on the connected card. In a cloud workspace, including when Desktop is attached to cloud, follow the sign-in link and tell the agent when you have connected. The agent never receives your token. The full steps are in Hosted and sandboxed connectors, and what each user sees after connecting is in OAuth connections.

Requirements to know up front

Calls that go through Harriet only allow public HTTPS. Harriet revalidates native MCP server URLs before each proxied call, which keeps the gateway from being used as a hop into internal networks. A server that only your computers can reach, such as a host on the office network, needs a direct connection from Harriet Desktop instead.

Sandboxed (npx / uvx) servers can tick Static outbound IP on the connector's Options tab so that server's outbound traffic leaves from Harriet's static outbound IP for sandboxed MCP servers, 52.208.246.51. Allowlist that address with the service the server calls. The address is shared by all Harriet customers who use it, so treat it as an extra check alongside credentials. Native MCP servers and OpenAPI connectors do not use it. Other connectors, such as HiBob and Workday, use a different address for their static IP option.

If your organization routes new connectors through review, a custom connector may start as a draft and need approval in the review queue before it can be deployed to devices.