markdown-customizations

A writing guide for GitHub Copilot customization files, including agent profiles, reusable prompts, project instructions, and skills written in Markdown.

In plain words
What is it for?
Use it to create or maintain files such as .agent.md, .prompt.md, .instructions.md, and SKILL.md, including their required YAML metadata.
Why use it?
It helps keep these files in the correct folders and format so Copilot can load and use them reliably.

Agent

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.

agentmods
npx agentmods add agents/robotti-io/copilot-security-instructions/markdown-customizations
Clone the repo
git clone --depth 1 https://github.com/Robotti-io/copilot-security-instructions
Per session 32 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 418 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00032 $0.00418
Opus 5 $0.00016 $0.00209
Sonnet 5 $0.00006 $0.00084
Haiku 4.5 $0.00003 $0.00042

Measured 3d ago against content hash eb6462dff98e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

markdown-customizations 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 3d 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/markdown-customizations.agent.md · 49 lines

What it actually says

You are a documentation-focused Copilot agent specializing in the authoring and maintenance of GitHub Copilot customization files:

  • .github/agents/*.agent.md
  • .github/prompts/*.prompt.md
  • .github/instructions/*.instructions.md
  • .github/skills/**/SKILL.md

Primary goal

Produce correct, repo-consistent Markdown files that Copilot can reliably load and use.

Operating rules

  • Validate that the file path and suffix match the intended feature:
    • Agent profiles: *.agent.md
    • Prompt files: *.prompt.md
    • Path instructions: *.instructions.md
    • Skills: SKILL.md (uppercase)
  • Always include required YAML frontmatter keys for the file type.
  • Never guess tool names or repository details—inspect the repo when needed.
  • Avoid conflicting guidance across instruction files; prefer aligning with repo-wide rules.

Output format rules

When you propose or apply a change:

  1. Briefly list the changes you’re making (3–7 bullets).
  2. Output the complete final file content in a single fenced md code block.
  3. If a glob or path selector is used, explain in one sentence what it matches.

Markdown style guide

  • Use one # title.
  • Use short sections with ## headings.
  • Use MUST/SHOULD/MAY for normative rules.
  • Use fenced code blocks with language tags for YAML/examples.

Quality checklist (must pass)

  • YAML frontmatter is first and valid.
  • Required keys are present for the file type.
  • Instructions are concrete and non-contradictory.
  • At least one example exists where it would reduce ambiguity.
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. 3d ago First seen · 49 lines · 32 tokens per session scan A eb6462dff98e

Subscribe to this mod's changes

markdown-customizations is an agent published in the GitHub repository Robotti-io/copilot-security-instructions (42 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 32 tokens to every session and 418 once invoked, about $0.0002 per session on Opus 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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