Connect your tools
Connect external services to Levin. Bring their tools into conversations and workflows.
MCP (Model Context Protocol) lets applications make tools available to an Agent. In Lévin™ Harness, Capabilities → MCP brings personal servers and plugin-provided servers into one view. Connect a service, inspect the tools it exposes, then make them available to the Agent.
Levin starts a local stdio command or connects to an SSE endpoint.
Once connected, Levin reads tool names, descriptions, parameters, and annotations.
Select a tool with @ in chat, or add it to a workflow.
Where services come from
The MCP list separates servers into Plugin and Personal groups. Both show connection status and tool count, but they are configured and managed differently.
| Source | How it enters Levin | What you can manage |
|---|---|---|
| Personal MCP | Add a stdio command or SSE endpoint from the MCP page. | Connect or disconnect, turn auto-connect on or off, view details, and delete the server. |
| Plugin MCP | Installed with a plugin that declares the service and its deployments. | View connections and tools. The plugin manages auto-connect and can group several deployments of one logical service. |
Use Personal MCP for services you maintain yourself. Use a plugin when the capability, runtime, and remote deployment need to travel together.
Add a personal MCP server
The setup screen currently supports two connection types: run a local stdio process, or connect to an SSE endpoint.
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1Open the setup screen
Go to Capabilities → MCP, then select Add server beside the Personal group.
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2Choose a transport
For stdio, enter a server name, command, and optional arguments. For SSE, enter a server name and URL.
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3Add and connect
Select Add server. Levin saves the configuration and immediately tries to start or connect to it.
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4Check discovery
Open the server details. Confirm that it is Connected, then review the tool count and parameters.
Setup fields
| Field | stdio | SSE |
|---|---|---|
| Server name | Required. Used in the list and capability picker. | Required. Used in the same places. |
| Transport | Levin starts a local command and exchanges messages over standard input and output. | Levin connects to a server-sent events endpoint. |
| Command / URL | Enter the command that starts the MCP process. | Enter the complete endpoint URL. |
| Arguments | Optional. Space-separated values passed to the command. | This field is not shown. |
Current form limits: the setup screen does not accept environment variables, a working directory, request headers, OAuth, or JSON imports. If an existing configuration or plugin definition includes a working directory, environment values, or remote runtime details, the server page still shows the configuration that is actually in use.
Connection status and server details
Each server updates its status in real time. Open it to control the connection, inspect its tool contracts, and confirm where the service is running.
| Status | What it means | What to do |
|---|---|---|
| Connecting / Reconnecting | Levin is starting the process or restoring the connection. | Wait for the status to update. There is no need to click Connect again. |
| Connected | The service is online. Levin reads and caches the tools it reports. | Expand the tools and review their descriptions, parameters, and annotations. |
| Stopped / Disconnected | No connection is available, so the service's tools do not appear in the picker. | Connect manually, or turn on auto-connect for a personal MCP server. |
| Error | The most recent start or connection failed. Details show the error. | Check the command, arguments, or SSE URL, then reconnect. |
What the details show
| Section | What you can inspect |
|---|---|
| Connection controls | Connect or disconnect. Personal MCP servers can use auto-connect; plugin MCP servers show that the plugin manages it. |
| Tools | Tool names, descriptions, input parameters, and required fields, discovered automatically after connection. |
| Tool annotations | When the service provides them, indicators for read-only, destructive, idempotent, and external-access behavior. |
| Configuration | Source, deployment, transport, execution location, and any configured endpoint, command, working directory, or environment-value count. Remote endpoints are hidden by default and can be revealed or copied. |
Use MCP tools in a task
MCP services that are enabled and recognized by Levin appear in the chat capability picker. Once connected, you can expand a service and choose one of its tools. The workflow editor reads available tools from the MCP servers that are currently connected.
- Confirm the connection. Open the server details, make sure it is connected, then expand the target tool and review its parameters.
- Choose where to use it. Type
@in chat, select the MCP server, then select a tool. Or add an MCP step to a workflow and set the server, tool, and parameters. - Set the task boundary. Tell Levin what to process, which objects it may affect, and what result you expect.
- Review the call. MCP tools run as standard Agent tools. Calls and results remain in the task record.
Connected does not mean approved. A connection makes the tools available. Every call still follows the current Agent's tool permissions and approval policy. Treat tool annotations from the MCP service as risk signals, not as a replacement for permissions.
Troubleshooting
The stdio service will not start
Run the same command and arguments in Terminal first. Confirm that the command exists, the arguments work, and the process implements the MCP protocol. The current setup screen does not provide working-directory or environment-variable fields.
The SSE service will not connect
Check the complete URL, network access, and the server's transport. The manual setup form supports SSE, so do not enter an endpoint that supports only a different HTTP transport.
The server is connected, but no tools appear
Reopen the server details and review the error. Confirm that the service completes tool discovery and reports at least one tool. If the list is still empty, disconnect and reconnect once.
The MCP tool is missing from chat
Return to Capabilities and confirm that the service is enabled, connected, and has discovered tools. For a plugin MCP server, also confirm that its deployment is online.