Meet Your Claw: A Harness in Three Lines of C#

dotnet demonstrates how to stand up an agent “harness” in C# using a single AsHarnessAgent call, then incrementally add tool calling, web search, and planning so a vague request becomes a tracked, step-by-step execution loop.

Overview

The video shows how to build a minimal agent harness in C# where a single call to AsHarnessAgent provides the core agentic loop.

Building blocks added to the harness

Ability 1: Custom tool for stock prices

• Adds a custom get_stock_price tool that the agent can call.

Ability 2: Built-in web search for market news

• Uses a built-in web search capability to pull market news relevant to a watchlist.

Ability 3: Planning with a to-do list

• Introduces planning via a to-do list.
• Uses both plan and execute modes to turn a vague request (for example, “review my watchlist and suggest something to add”) into a tracked, step-by-step plan.

Wiring and running the agent

• Wires the agent to a Microsoft Foundry chat client.
• Runs the agent in the shared harness console.
• Sets up a companion repo so everyone starts on the same SDK version.

Resources

• Series info: https://aka.ms/FMTA/series
• Agent harness resource: https://aka.ms/AgentHarness