mcp-example

harness install mcp-example

The mcp-example package is an example of a package that adds an MCP server as a connector: a small unit-conversion server whose one tool the agent's programs can call.

Install

harness install mcp-example

It needs nothing outside Python.

Use

The package adds the service mcp-units, an MCP server over streamable HTTP. Start it, then give an agent the server and the mcp skill:

harness up mcp-units

[services]
mcp = ["mcp-units"]

[skills]
enable = ["mcp"]

A program then lists and calls its tools:

print(mcp_tools())
mcp_call("convert", value=3, from_unit="in", to_unit="cm")    # 7.62

In the app, add the running server under Settings → Connectors → Your own server with its URL, http://localhost:8860/mcp; Tools lists what it offers.

What it provides

• Service mcp-units: an MCP server with one tool, convert(value, from_unit, to_unit), between units of length (m, cm, mm, in), mass (kg, g, lb) and angle (rad, deg).
• Skill mcp: mcp_tools() lists every tool of the agent's MCP servers; mcp_call(tool, **arguments) calls one.

Make your own

Copy the package and replace the server. Any MCP server with the streamable HTTP transport is added the same way: a service manifest of kind mcp with its command (or the URL of a server that already runs) and a client URL. A server that only speaks stdio runs behind an HTTP bridge as a service. See Services and Packages.

Limits and known issues

An MCP server runs outside the programs' sandbox: whatever its tools reach, programs reach through mcp_call. Give an agent only servers whose tools are safe for any program to call.

0.1.0

• First release as a package of its own (moved out of the harness core).