---
title: Agent
order: 1
description: "A model working through an agent host such as Claude Code, Codex, Cursor or OpenCode. magus treats an agent as one more caller of its CLI, MCP tools and console, held to the same checks as a person."
tags: [glossary, agents]
---

# Agent

A model working through an agent host such as Claude Code, Codex, Cursor or
OpenCode: it reads, decides and calls tools inside the host's loop. magus
treats an agent as one more caller of its CLI, MCP tools and console, held to
the same guard and the same checks as a person. magus does not run, prompt or
route an agent; the host does.

## Elsewhere

Anthropic describes agents as systems where a model directs its own process and tool use,
as opposed to a workflow that follows fixed code paths. The Mastra TypeScript SDK and the
OpenAI Agents SDK each make an agent an object that bundles a model, instructions and tools
(`new Agent({ name, instructions, model, tools })` in Mastra). magus builds no agent object
and keeps no loop: an agent is whoever the host runs, and magus answers it.

## Example

`magus agent install` writes the skills, hooks and MCP wiring each host reads.

```sh
magus agent install
```

## Used in

<!-- BEGIN GLOSSARY USAGE (generated by glossary-usage-generate from the knowledge graph; edit the generator, not this list) -->

In the docs:

- [The agent harness benchmark](../benchmarks.md#the-agent-harness-benchmark)
- [Agent contact (@session)](../concepts/knowledge.md#agent-contact-session)
- [An outline from an agent](../concepts/review.md#an-outline-from-an-agent)
- [Practices for agent-run work](../decisions/0005-deterministic-answers.md#practices-for-agent-run-work)
- [ADR 0009: cost profiles for agent sessions](../decisions/0009-cost-profiles-for-agent-sessions.md#adr-0009-cost-profiles-for-agent-sessions)
- [A harness is not an agent thing](../design/principles/a-harness-is-not-an-agent-thing.md#a-harness-is-not-an-agent-thing)

In the code (`magus refs <name>` lists every site):

- `agent.Agent` (Go)
- `sessions.Agent` (Go)

<!-- END GLOSSARY USAGE -->

## See also

- [Harness](harness.md)
- [Tool](tool.md)
- [Skill](skill.md)
- [Session](session.md)