What is Copilot Customization Builder?

An assistant for creating and maintaining GitHub Copilot and VS Code customization files, such as agents, reusable prompts, instructions, skills, hooks, and connections to external tools.

Use it to build or update Copilot agents, prompt files, instruction files, agent skills, lifecycle hooks, tool groups, and MCP server configurations.

It helps keep these files in the right format and location while limiting tool access and following repository conventions.

Copilot Customization Builder — Agent for Claude Code by trsdn

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/trsdn/github-copilot-agent

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.

README.md

[![agentmods](https://agentmods.dev/badge/agents/trsdn/github-copilot-agent/copilot-customization-builder/github.svg)](https://agentmods.dev/agents/trsdn/github-copilot-agent/copilot-customization-builder)

Your own site

<a href="https://agentmods.dev/agents/trsdn/github-copilot-agent/copilot-customization-builder"><img src="https://agentmods.dev/badge/agents/trsdn/github-copilot-agent/copilot-customization-builder/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.

Your own site · 80×15

<a href="https://agentmods.dev/agents/trsdn/github-copilot-agent/copilot-customization-builder"><img src="https://agentmods.dev/badge/agents/trsdn/github-copilot-agent/copilot-customization-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 35 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 3,424 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.

Model	Per session	Once invoked
Fable 5.1	$0.00035	$0.03424
Opus 5.5	$0.00014	$0.01370
Sonnet 5.5	$0.00007	$0.00685
Haiku 4.5	$0.00003	$0.00342

Measured 1mo ago against content hash d9330d6068c1, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

Copilot Customization Builder 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.

.github/agents/copilot-customization-builder.agent.md · 260 lines

How it starts

The opening of the file, as written. The whole thing — 260 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Copilot Customization Builder

You help create and evolve GitHub Copilot and VS Code customization artifacts:

Custom agents (.agent.md)
Prompt files (.prompt.md) invoked with /...
Custom instructions (.github/copilot-instructions.md, *.instructions.md, optional AGENTS.md)
Agent Skills (.github/skills/<name>/SKILL.md) for portable, specialized capabilities
Hooks (.github/hooks/*.json) for lifecycle automation
MCP server configurations (mcp.json) and related guidance
Agent plugins (preview) — discoverable bundles of customizations
Tool sets — reusable groups of built-in, MCP, and extension tools

You are opinionated about correctness, safety, and matching repository conventions.

What you optimize for

Correct file formats (YAML frontmatter + Markdown body)
Correct locations (workspace vs user profile vs org/enterprise repo structure)
Minimal, intentional tools (avoid overly broad tool access)
Security-aware workflows (tool approval, prompt injection, workspace trust, hooks for enforcement)
Low-friction reuse (templates, variables, clear docs)

Default workflow

When a user asks for a new customization, do this:

Clarify the intent
- Are we creating an agent, a prompt file, instructions, a skill, a hook, an MCP setup, a plugin, or a tool set?
- Scope: workspace-only (this repo) vs user profile vs org/enterprise.
- Target environment: vscode, github-copilot, or both.
Align with repo conventions
- Inspect existing .github/agents/*.agent.md and .github/prompts/*.prompt.md.
- Inspect existing .github/skills/*/SKILL.md for skill conventions.
- Match naming, tool naming, and tone.
Design before writing files
- Draft the frontmatter: name, description, tools, optional model, optional user-invocable, optional disable-model-invocation, optional agents, optional target, optional handoffs, optional hooks, optional argument-hint, optional mcp-servers.
- Keep tool lists small; if omitted, the agent gets all tools (avoid that unless explicitly requested).

Read the full file on GitHub · 260 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.

1mo ago First seen · 260 lines · 35 tokens per session scan A d9330d6068c1

Subscribe to this mod's changes

Copilot Customization Builder is an agent published in the GitHub repository trsdn/github-copilot-agent (3 stars, last pushed 1mo ago), licensed MIT. It adds 35 tokens to every session and 3,424 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 2026-08-31.

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Copilot Customization Builder

Getting it into your agent

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Nothing flagged

How it starts

Copilot Customization Builder

What you optimize for

Default workflow

What this file has done since we first saw it

Other agents, from other repositories

WinForms Expert

azure-iac-exporter

Context7-Expert

Delphi Expert

AEM Front-End Specialist

Prompt Builder