# Update Agent

> Create, update, or manage universal-ai-config agent templates. Handles finding existing agents, deciding whether to create or modify, and writing the template.

- Skill: `fabis94/update-agent` (Agent Skill)
- Install (CLI): `npx skillmds@latest add fabis94/update-agent`
- Raw SKILL.md: https://api.skillmd.com/api/skills/fabis94/update-agent/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: fabis94 (https://skillmd.com/u/fabis94)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/fabis94/update-agent

---


# Manage Agent Templates

Agents are specialized AI personas with scoped tools and permissions that run in isolated contexts.

**Important:** Agents are supported by Claude, Copilot, and Codex. Cursor does not support agents — consider using a skill with `forkContext: true` as an alternative for Cursor. Codex emits each agent as a standalone `.codex/agents/<name>.toml` file (body becomes `developer_instructions`); see the "Codex caveats" section in `<%= instructionPath('uac-template-guide') %>`.

## Finding Existing Agents

List files in `<%= agentTemplatePath() %>/` to discover existing agent templates. Read their frontmatter to understand each agent's purpose and capabilities.

## Deciding What to Do

- **Create new**: when you need a new specialized persona with distinct capabilities
- **Update existing**: when an agent needs adjusted tools, permissions, or system prompt
- **Delete**: when an agent is no longer needed

## Creating a New Agent

1. Create a `.md` file in `<%= agentTemplatePath() %>/` with a descriptive name (e.g. `code-reviewer.md`)
2. Add YAML frontmatter with at minimum `name` and `description`
3. Write the agent's system prompt as the body

### Frontmatter Fields

See the **Agents** section in `<%= instructionPath('uac-template-guide') %>` for the complete field reference and per-target override syntax. Key fields: `name`, `description`, `model`, `tools`, `permissionMode`, `hooks`, plus Codex-specific `nicknameCandidates` and `sandboxMode`.

### Cross-target gotchas for agents

When targeting Codex alongside Claude/Copilot, three fields require special attention because their vocabularies don't align (see "Cross-target value gotchas" in `<%= instructionPath('uac-template-guide') %>`):

- **`model`**: Use a per-target override. Claude takes `claude-*` model IDs; Codex takes `gpt-5.4`, `gpt-4.1`, etc.
- **`permissionMode` vs `sandboxMode`**: `permissionMode` is Claude-specific (`acceptEdits`, `bypassPermissions`, `plan`). For Codex, set `sandboxMode: { codex: "workspace-write" }` (values: `read-only`, `workspace-write`, `danger-full-access`).
- **`tools`**: Codex has no agent-level tool restriction — configure per-server `enabledTools` on the MCP server config instead. Universal `tools` is dropped for Codex with a warning.

### Example

```markdown
---
name: security-reviewer
description: Reviews code for security vulnerabilities and best practices. Use proactively after code changes.
tools: ["Read", "Grep", "Glob", "Bash"]
model: sonnet
---

You are a security-focused code reviewer. When invoked:

1. Identify the changed files
2. Check for common vulnerabilities (injection, XSS, auth issues)
3. Review dependency usage for known CVEs
4. Report findings by severity (critical, warning, info)
```