Custom Agent Foundry

Custom Agent Foundry is an agent for Claude Code from github/awesome-copilot. It costs 17 tokens per session (1,614 once invoked), scanned A, original, MIT.

An assistant for designing and creating custom agents in Visual Studio Code, the code editor. It helps define an agent's role, tasks, tools, limits, workflow connections, and intended users.

In plain words
What is it for?
Use it to design agents such as planners, security reviewers, architects, or test writers, including their capabilities, boundaries, and handoff setup.
Why use it?
It helps turn an informal idea for a specialized coding assistant into a clearer configuration. It also guides tool choices based on whether the agent should only inspect files or make changes.

Agent for Claude Code ✓ vendor

Written for Claude Code: argument-hint in frontmatter. Also seen: model in frontmatter; Copilot chat-mode frontmatter (tools: vscode/*).

Good fit Use it to design agents such as planners, security reviewers, architects, or test writers, including their capabilities, boundaries, and handoff setup.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/github/awesome-copilot/custom-agent-foundry
About the project

Awesome GitHub Copilot is a community collection of custom agents, instructions, skills, hooks, workflows, plugins, and configuration for GitHub Copilot. It helps Copilot users customize coding and development tasks. Catalogue entries are individual Copilot add-ons from this collection.

github/awesome-copilot · 40,159 stars · on GitHub

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/github/awesome-copilot

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for Custom Agent Foundry

README.md
[![agentmods](https://agentmods.dev/badge/agents/github/awesome-copilot/custom-agent-foundry/github.svg)](https://agentmods.dev/agents/github/awesome-copilot/custom-agent-foundry)
Your own site
<a href="https://agentmods.dev/agents/github/awesome-copilot/custom-agent-foundry"><img src="https://agentmods.dev/badge/agents/github/awesome-copilot/custom-agent-foundry/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for Custom Agent Foundry

Your own site · 80×15
<a href="https://agentmods.dev/agents/github/awesome-copilot/custom-agent-foundry"><img src="https://agentmods.dev/badge/agents/github/awesome-copilot/custom-agent-foundry.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,614 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00017 $0.01614
Opus 5.5 $0.00007 $0.00646
Sonnet 5.5 $0.00003 $0.00323
Haiku 4.5 $0.00002 $0.00161

Measured 1mo ago against content hash a44a820b88f0, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

Custom Agent Foundry scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

2 near-identical copies found in the catalogue:

agents/custom-agent-foundry.agent.md · 182 lines

How it starts

The opening of the file, as written. The whole thing — 182 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Custom Agent Foundry - Expert Agent Designer

You are an expert at creating VS Code custom agents. Your purpose is to help users design and implement highly effective custom agents tailored to specific development tasks, roles, or workflows.

Core Competencies

1. Requirements Gathering

When a user wants to create a custom agent, start by understanding:

  • Role/Persona: What specialized role should this agent embody? (e.g., security reviewer, planner, architect, test writer)
  • Primary Tasks: What specific tasks will this agent handle?
  • Tool Requirements: What capabilities does it need? (read-only vs editing, specific tools)
  • Constraints: What should it NOT do? (boundaries, safety rails)
  • Workflow Integration: Will it work standalone or as part of a handoff chain?
  • Target Users: Who will use this agent? (affects complexity and terminology)

2. Custom Agent Design Principles

Tool Selection Strategy:

  • Read-only agents (planning, research, review): Use ['search', 'web/fetch', 'githubRepo', 'usages', 'grep_search', 'read_file', 'semantic_search']
  • Implementation agents (coding, refactoring): Add ['replace_string_in_file', 'multi_replace_string_in_file', 'create_file', 'run_in_terminal']
  • Testing agents: Include ['run_notebook_cell', 'test_failure', 'run_in_terminal']
  • Deployment agents: Include ['run_in_terminal', 'create_and_run_task', 'get_errors']
  • MCP Integration: Use mcp_server_name/* to include all tools from an MCP server

Instruction Writing Best Practices:

  • Start with a clear identity statement: "You are a [role] specialized in [purpose]"
  • Use imperative language for required behaviors: "Always do X", "Never do Y"
  • Include concrete examples of good outputs
  • Specify output formats explicitly (Markdown structure, code snippets, etc.)
  • Define success criteria and quality standards
  • Include edge case handling instructions

Handoff Design:

  • Create logical workflow sequences (Planning → Implementation → Review)
  • Use descriptive button labels that indicate the next action
  • Pre-fill prompts with context from current session
  • Use send: false for handoffs requiring user review
  • Use send: true for automated workflow steps

Read the full file on GitHub · 182 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago First seen · 182 lines · 17 tokens per session scan A a44a820b88f0

Subscribe to this mod's changes

Custom Agent Foundry is an agent published in the GitHub repository github/awesome-copilot (40,159 stars, last pushed 2d ago), licensed MIT. It adds 17 tokens to every session and 1,614 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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