# I Built a GitHub Action That Writes Your PR Descriptions

> Source: <https://dev.to/xenocyber0/i-built-a-github-action-that-writes-your-pr-descriptions-2obp>
> Published: 2026-08-10 21:06:48+00:00

Yep, this does what the title says. StandupBot reads the actual PR diff and commit messages, runs them through any OpenAI-compatible LLM endpoint, and writes a structured Summary / Changes / Testing description — so you never have to write "fixed stuff" again.

I built this for my own team because I was tired of staring at empty PR boxes after every fix. Then I put it on GitHub Marketplace so anyone can use it. MIT licensed, no strings.

A GitHub Action that writes your PR descriptions for you. It runs the real diff and commits through an LLM you choose, and fills in a structured **Summary / Changes / Testing** description plus up to three labels — so you stop hand-writing PR bodies and standup updates.

Bring your own model: it talks to **any OpenAI-compatible endpoint** (OpenAI, OpenRouter, Ollama, LM Studio, …). No provider, URL, or model is hardcoded.

Generated end-to-end by StandupBot for a real PR ([nodejs/node#64573](https://github.com/nodejs/node/pull/64573)) from its actual diff, using a real LLM endpoint. This is the description it produced verbatim:

## Summary

Add

`lchownSync`

to the VFS implementation so that symbolic link ownership can be changed without following the link, matching the behavior of`fs.lchownSync`

.## Changes

- doc/api/vfs.md: added
`lchownSync(path, uid, gid)`

to the list of VFS API signatures.- lib/internal/vfs/file_system.js: added synchronous
`lchownSync`

method to`VirtualFileSystem`

and updated the async…

You open a PR. Forty files changed. Two hours of focused work. The description field is empty.

So you write: `fixed stuff`

. Or `updated code`

. Or `changes requested by reviewer`

.

Three months later, someone (you) is running `git log -p`

trying to figure out why the config format changed in April. The PR description was supposed to save that investigation. Nobody wrote it.

We tried before:

| Approach | Why it failed |
|---|---|
| PR templates | Everyone types "see title" into the template |
| Checklist bots | Nagging doesn't scale; people ignore them |
| Reviewer enforcement | Becomes the team's most hated job |

The gap isn't discipline. It's that writing PR descriptions is **unrewarded work**. You get the same merge button whether you write a detailed description or "fixed stuff."

So I built [StandupBot](https://github.com/marketplace/actions/standupbot-pr-describer).

This is verbatim output from [nodejs/node#64573](https://github.com/nodejs/node/pull/64573), generated from the actual diff:

## Summary

Add

`lchownSync`

to the VFS implementation so that symbolic link ownership can be changed without following the link, matching the behavior of`fs.lchownSync`

.## Changes

- doc/api/vfs.md: added
`lchownSync(path, uid, gid)`

to VFS API signatures.- lib/internal/vfs/file_system.js: added synchronous
`lchownSync`

method and updated the async wrapper.- lib/internal/vfs/provider.js: added default
`lchownSync`

method with JSDoc comment.- lib/internal/vfs/providers/memory.js: implemented
`lchownSync`

that updates uid/gid of the link entry.- lib/internal/vfs/setup.js: changed handler to invoke
`vfs.lchownSync`

instead of`vfs.chownSync`

.- test/parallel/test-vfs-lchown-symlink.js: new test verifying sync, callback, and promise variants.
## Testing

The new test exercises

`fs.lchownSync`

,`fs.lchown`

(callback), and`fsp.lchown`

(promise) on symlinks inside a VFS mount, asserting correct uid/gid changes.

Nobody edited that. It went straight from the model into the PR body. The action also returns a normalized `title`

and `labels`

clamped to `bug | feature | chore | docs | refactor`

— so your label taxonomy stays clean.

Add `.github/workflows/standupbot.yml`

:

```
name: StandupBot
on:
  pull_request:
    types: [opened, synchronize]

permissions:
  pull-requests: write
  contents: read

jobs:
  describe:
    runs-on: ubuntu-latest
    steps:
      - uses: XenoCyber0/StandUpBot@v1
        with:
          llm-base-url: ${{ secrets.LLM_BASE_URL }}
          llm-api-key: ${{ secrets.LLM_API_KEY }}
          model: ${{ vars.LLM_MODEL }}
```

Set `LLM_API_KEY`

as a **secret**, `LLM_MODEL`

as a **variable**. That's the whole thing.

The action talks to **any** OpenAI-compatible chat API. Nothing is hardcoded. All of these work:

```
OpenAI        → https://api.openai.com/v1
OpenRouter    → https://openrouter.ai/api/v1
Ollama        → http://localhost:11434/v1
LM Studio     → http://localhost:1234/v1
LocalAI       → http://localai:8080/v1
You decide.
```

You pick the model. You control the data path. Switching providers later is one secret update.

If you want your code to never leave your network:

```
GitHub repo ──webhook──▶ self-hosted Actions runner ──HTTP──▶ Ollama
                             (on your LAN)              (your LLM box)
```

`llm-base-url`

at your Ollama/LM Studio instance`llm-api-key`

can be any non-empty string — Ollama ignores itYour diff never crosses the internet. The only outbound call is writing the PR body back to GitHub, which... GitHub already owns.

**Model notes:** In my testing, **Qwen2.5-Coder 7B** and similar 7–9B instruction-tuned models work well. Below ~3B params, file-name hallucinations start appearing.

The rule is simple:

Your hand-written descriptions are safe. If you ever overwrite what it generated, it takes the hint and stays out.

Three parts worth stealing:

**1. Diff budget.** Fetches the PR diff, applies gitignore-style exclusions from `.standupbot.yml`

before anything hits a prompt:

```
exclude:
  - package-lock.json
  - '**/*.lock'
  - '**/dist/**'
```

The diff is hard-capped at ~24KB — a monster PR can't blow up your LLM context window.

**2. Map-reduce for big diffs.** Under the budget, one call. Over it? Each file gets summarized individually (max 8 LLM calls), then merged into the final description.

**3. Structured output enforcement.** The prompt requires a rigid schema — `title`

, `summary`

, `changes[]`

, `testing`

, `labels[]`

— and the parser clamps labels to the allowed set. If the model invents `urgent-pls`

, it gets dropped, not shipped.

**Marketplace:** [github.com/marketplace/actions/standupbot-pr-describer](https://github.com/marketplace/actions/standupbot-pr-describer)

**Source:** [github.com/XenoCyber0/StandUpBot](https://github.com/XenoCyber0/StandUpBot) (MIT)

**Issues/feedback:** [github.com/XenoCyber0/StandUpBot/issues](https://github.com/XenoCyber0/StandUpBot/issues)

Written by the person who finally read "fixed stuff" one too many times and decided to do something about it.