hermes-agent/optional-skills/devops/watchers/SKILL.md
Teknium ea8e608821
feat(skills): watchers skill — poll RSS / HTTP JSON / GitHub via cron no-agent (#21881)
* feat(skills): watchers skill — poll RSS / HTTP JSON / GitHub via cron no-agent

Ships three reusable polling scripts plus a shared watermark helper as an
optional skill.  Users wire them into the existing cron (no_agent=True)
mode rather than learning a new subsystem.

Supersedes the closed PR #21497 (parallel watcher subsystem).  Same value,
zero new core surface.

## What ships

- optional-skills/devops/watchers/SKILL.md: pattern + three example cron commands
- optional-skills/devops/watchers/scripts/_watermark.py: shared helper
  (atomic state writes, bounded ID set, first-run baseline)
- optional-skills/devops/watchers/scripts/watch_rss.py: RSS 2.0 + Atom
- optional-skills/devops/watchers/scripts/watch_http_json.py: any JSON endpoint
  with configurable id_field / items_path / headers
- optional-skills/devops/watchers/scripts/watch_github.py: issues / pulls /
  releases / commits (uses GITHUB_TOKEN if present)

## Invariants enforced by the shared helper

- First run records baseline, emits nothing (never replays existing feed)
- Watermark file is <state_dir>/<name>.json, atomic replace on write
- Bounded to 500 IDs (configurable)
- Empty stdout when no new items — cron treats that as silent delivery

## Validation
- watch_rss.py against news.ycombinator.com/rss first run → empty stdout, watermark populated
- Removed one seen-id, second run → emitted exactly that item
- No DeprecationWarnings (ET element truth-value footgun dodged explicitly)

End-user pattern: 'hermes cron create my-feed --schedule "*/15 * * * *" --no-agent --script $HERMES_HOME/skills/devops/watchers/scripts/watch_rss.py --script-args "--name hn --url https://news.ycombinator.com/rss" --deliver telegram'

* docs(skills/watchers): tighten description to match peer optional skills

* docs(skills/watchers): align frontmatter + structure with peer optional skills

* docs(skills/watchers): gate to linux/macos (shell syntax in examples)
2026-05-08 09:27:15 -07:00

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Markdown

---
name: watchers
description: Poll RSS, JSON APIs, and GitHub with watermark dedup.
version: 1.0.0
author: Hermes Agent
license: MIT
platforms: [linux, macos]
metadata:
hermes:
tags: [cron, polling, rss, github, http, automation, monitoring]
category: devops
requires_toolsets: [terminal]
related_skills: []
---
# Watchers
Poll external sources on an interval and react only to new items. Three ready-made scripts plus a shared watermark helper; wire them into a cron job (or run them ad-hoc from the terminal).
## When to Use
- User wants to watch an RSS/Atom feed and be notified of new entries
- User wants to watch a GitHub repo's issues / pulls / releases / commits
- User wants to poll an arbitrary JSON endpoint and get notified on new items
- User asks for "a watcher for X" or "notify me when X changes"
## Mental model
A watcher is just a script that:
1. Fetches data from the external source
2. Compares against a watermark file of previously-seen IDs
3. Writes the new watermark back
4. Prints new items to stdout (or nothing on no-change)
The scripts below handle all three. The agent runs them via the terminal tool — from a cron job, a webhook, or an interactive chat — and reports what's new.
## Ready-made scripts
All three live in `$HERMES_HOME/skills/devops/watchers/scripts/` once the skill is installed. Each reads `WATCHER_STATE_DIR` (defaults to `$HERMES_HOME/watcher-state/`) for its state file, keyed by the `--name` argument.
| Script | What it watches | Dedup key |
|---|---|---|
| `watch_rss.py` | RSS 2.0 or Atom feed URL | `<guid>` / `<id>` |
| `watch_http_json.py` | Any JSON endpoint returning a list of objects | Configurable id field |
| `watch_github.py` | GitHub issues / pulls / releases / commits for a repo | `id` / `sha` |
All three:
- First run records a baseline — never replays existing feed
- Watermark is a bounded ID set (max 500) to cap memory
- Output format: `## <title>\n<url>\n\n<optional body>` per item
- Empty stdout on no-new — the caller treats that as silent
- Non-zero exit on fetch errors
## Usage
Run a watcher directly from the terminal tool:
```bash
python $HERMES_HOME/skills/devops/watchers/scripts/watch_rss.py \
--name hn --url https://news.ycombinator.com/rss --max 5
```
Watch a GitHub repo (set `GITHUB_TOKEN` in `~/.hermes/.env` to avoid the 60 req/hr anonymous rate limit):
```bash
python $HERMES_HOME/skills/devops/watchers/scripts/watch_github.py \
--name hermes-issues --repo NousResearch/hermes-agent --scope issues
```
Poll an arbitrary JSON API:
```bash
python $HERMES_HOME/skills/devops/watchers/scripts/watch_http_json.py \
--name api --url https://api.example.com/events \
--id-field event_id --items-path data.events
```
## Wiring into cron
Ask the agent to schedule a cron job with a prompt like:
> Every 15 minutes, run `watch_rss.py --name hn --url https://news.ycombinator.com/rss`. If it prints anything, summarize the headlines and deliver them. If it prints nothing, stay silent.
The agent invokes the script via the terminal tool inside the cron job's agent loop; no changes to cron's built-in `--script` flag are needed.
## State files
Every watcher writes `$HERMES_HOME/watcher-state/<name>.json`. Inspect:
```bash
cat $HERMES_HOME/watcher-state/hn.json
```
Force a replay (next run treated as first poll):
```bash
rm $HERMES_HOME/watcher-state/hn.json
```
## Writing your own
All three scripts use the same template: load watermark, fetch, diff, save, emit. `scripts/_watermark.py` is the shared helper; import it to get atomic writes + bounded ID set + first-run baseline for free. See any of the three reference scripts for how little boilerplate it takes.
## Common Pitfalls
1. **Printing a "no new items" header every tick.** Callers rely on empty stdout = silent. If you print anything on an empty delta, you spam the channel. The shipped scripts handle this; custom scripts must too.
2. **Expecting the first run to emit items.** It won't — first run records a baseline. If you need an initial digest, delete the state file after the first run or add a `--prime-with-latest N` flag in your own script.
3. **Unbounded watermark growth.** The shared helper caps at 500 IDs. Raise it for high-churn feeds; lower it on constrained filesystems.
4. **Putting the state dir where the agent's sandbox can't write.** `$HERMES_HOME/watcher-state/` is always writable. Docker/Modal backends may not see arbitrary host paths.