---
title: "Harness Context Protocol"
description: "Harness Context Protocol is the open standard for installing capabilities into any agent harness. A Harness Pack is three files (a manifest of named commands, a policy, and a skill) that a runtime can lint, authorise, and execute."
canonical: https://harnesscontextprotocol.dev/
---

# Harness Context Protocol

> Harness Context Protocol is the open standard for installing capabilities into any agent harness. A Harness Pack is three files (a manifest of named commands, a policy, and a skill) that a runtime can lint, authorise, and execute.

Skills teach. MCP connects. HCP installs.

Protocol version: HCP/1.1 (Draft). Vendor-neutral open specification.

A **Harness Pack** is three files: named commands (`surface.json`), a policy (`policy.json`), and a skill (`HARNESS.md`). A runtime lints, authorises, and executes it.

## Three jobs. Three standards.

- [Agent Skills](https://agentskills.io) teach — prose that tells an agent how to behave. No execution, no permissions, no secrets.
- [MCP](https://modelcontextprotocol.io) connects — a transport between a model and a tool.
- [HCP](https://harnesscontextprotocol.dev/docs/introduction/what-is-hcp) installs — a CLI becomes an installable unit with named commands, Binding, Policy, Sense, and a Skill.

If Skills are the manual and MCP is the cable, HCP is the appliance you plug in.

## Two loops, one pack

- [Execute](https://harnesscontextprotocol.dev/docs/specification/execute) — inbound named CLI commands with a JSON twin, run under Policy.
- [Sense](https://harnesscontextprotocol.dev/docs/specification/sense) — outbound triggers. Observation cannot turn into an action on its own.

## Start here

- [Quickstart](https://harnesscontextprotocol.dev/docs/quickstart.md)
- [What is HCP?](https://harnesscontextprotocol.dev/docs/introduction/what-is-hcp.md)
- [Specification](https://harnesscontextprotocol.dev/docs/specification.md)
- [Glossary](https://harnesscontextprotocol.dev/docs/reference/glossary.md)
- [SDK](https://harnesscontextprotocol.dev/docs/reference/sdk.md)

## For agents

- [llms.txt](https://harnesscontextprotocol.dev/llms.txt) — curated index
- [llms-full.txt](https://harnesscontextprotocol.dev/llms-full.txt) — every page as markdown
- [MCP server](https://harnesscontextprotocol.dev/mcp) — list, search, and read pages
- [OpenAPI](https://harnesscontextprotocol.dev/openapi.json) — HTTP surface
- [AGENTS.md](https://harnesscontextprotocol.dev/AGENTS.md) — how to work this site

## Sitemap

- [Home](https://harnesscontextprotocol.dev/)
- [Documentation](https://harnesscontextprotocol.dev/docs)
- [Glossary](https://harnesscontextprotocol.dev/docs/reference/glossary)
- [llms.txt](https://harnesscontextprotocol.dev/llms.txt)
- [llms-full.txt](https://harnesscontextprotocol.dev/llms-full.txt)
- [OpenAPI](https://harnesscontextprotocol.dev/openapi.json)
- [MCP](https://harnesscontextprotocol.dev/mcp)