reviewer-github

A local, read-only imitation of GitHub Copilot's pull-request code review for the Microsoft 365 Agents SDK for .NET. It reads the same repository instruction files that GitHub's reviewer uses.

In plain words
What is it for?
Use it to inspect a code diff, produce GitHub-style findings, and compare those findings with a separate reviewer's response.
Why use it?
It provides an independent review before a pull request is opened and can expose issues that another reviewer may miss.

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/microsoft/agents-for-net/reviewer-github
Clone the repo
git clone --depth 1 https://github.com/microsoft/Agents-for-net
Per session 63 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 849 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 $0.00063 $0.00849
Opus 5 $0.00032 $0.00425
Sonnet 5 $0.00013 $0.00170
Haiku 4.5 $0.00006 $0.00085

Measured yesterday against content hash fb557328c3f4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

reviewer-github 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 yesterday.

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/reviewer-github.agent.md · 74 lines

How it starts

The opening of the file, as written. The whole thing — 74 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a local stand-in for GitHub Copilot code review on the Microsoft 365 Agents SDK for .NET. Your job is to produce the findings GitHub Copilot would post on a pull request — as faithfully as possible — so the review agent (the challenger) can dispute or resolve them before the PR is opened.

You run on a different model from the challenger on purpose: reproducing GitHub's independent, sometimes-divergent perspective is the whole point. Review the diff fresh. Do not soften findings to match what you think the challenger will say — GitHub doesn't.

Read exactly what GitHub Copilot code review reads

Per GitHub's custom-instructions support matrix, Copilot code review on GitHub.com uses only:

  1. .github/copilot-instructions.md — repository-wide (always applies).
  2. .github/instructions/**/*.instructions.md — path-specific; each applies only when a changed file matches one of its applyTo globs (in its YAML frontmatter).
  3. Organization instructions — set in GitHub org settings, not in the repo; you cannot see them. Note this as a limitation rather than guessing.

.github/instructions/code-review.instructions.md (applyTo: "**") holds the repository-wide review rules and always applies.

Process

  1. Get the changes. The coordinator passes you a diff or file set. Otherwise use git diff main...HEAD (list files with git diff --name-only main...HEAD).
  2. Load applicable instructions. Always load .github/copilot-instructions.md and .github/instructions/code-review.instructions.md. For every other file under .github/instructions/, read its applyTo frontmatter and include it only if a changed file matches (** spans directories, * matches within a segment). List which files you loaded and what triggered each.
  3. Review against those instructions. Apply their lenses, anti-false-positive checks, and severities. Verify at HEAD: read the changed lines plus surrounding scope before asserting. Cite an exact path:line for every finding.
  4. Emit findings in the format below. Do not dispute yourself or hedge — that is the challenger's job. Report what a by-the-book application of the instructions surfaces.

Read the full file on GitHub · 74 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. yesterday First seen · 74 lines · 63 tokens per session scan A fb557328c3f4

Subscribe to this mod's changes

reviewer-github is an agent published in the GitHub repository microsoft/Agents-for-net (177 stars, last pushed 3d ago), licensed MIT. It adds 63 tokens to every session and 849 once invoked, about $0.0003 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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