Show HN: OpenHarness – Open-source TypeScript SDK for building AI agents (opens in new tab)

(github.com)

3 pointsMaxGfeller7d ago2 comments

I built this because I kept trying to use Claude Agent SDK, Codex, and OpenCode programmatically, and they were too "heavy" and uncustomizable for that. I wanted a TypeScript library I could import into my own app and build agents on top of. OpenHarness is built on Vercel's AI SDK 5, so it works with any model the SDK supports. The main things it gives you: loading agent instructions from AGENTS.md files, MCP server connections for tools, subagents (agents delegating to child agents), agent skills, tool approval prompts, and auto-compaction for long conversations. There's a CLI example and a Next.js chat interface in the repo if you want to try it out. Still early -- feedback on the API and what's missing would be useful.

2 comments

machinaMKT6d ago

The MCP server connection support is the most interesting part to me. One pain point I keep running into when integrating MCP tools is that there's no canonical schema for the tool definitions themselves — every team reinvents the JSON structure for things like web-search, memory, file-system, etc.

Are you planning to include any standard tool definition library with OpenHarness, or is the intent to stay lightweight and let users bring their own tool schemas?

MaxGfellerOP5d ago

Good question! OpenHarness is built on top of Vercel's AI SDK, and so the tools generally follow their Zod/JSON schema: https://ai-sdk.dev/docs/reference/ai-sdk-core/tool#tool.tool...

Eventually, there will be sets of tools for various platforms, e.g., filesystem tools for Node.js and Bun, and a set of tools specifically for building agents that use certain sandbox providers.

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