Watchers — Poll RSS, JSON APIs, and GitHub with watermark dedup

Poll RSS, JSON APIs, and GitHub with watermark dedup.

Skill metadata


Source	Optional — install with `hermes skills install official/devops/watchers`
Path	`optional-skills/devops/watchers`
Version	`1.0.0`
Author	Hermes Agent
License	MIT
Platforms	linux, macos
Tags	`cron`, `polling`, `rss`, `github`, `http`, `automation`, `monitoring`

Reference: full SKILL.md

The following is the complete skill definition that Hermes loads when this skill is triggered. This is what the agent sees as instructions when the skill is active.

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:

Fetches data from the external source
Compares against a watermark file of previously-seen IDs
Writes the new watermark back
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:

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):

python $HERMES_HOME/skills/devops/watchers/scripts/watch_github.py \
  --name hermes-issues --repo NousResearch/hermes-agent --scope issues

Poll an arbitrary JSON API:

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:

cat $HERMES_HOME/watcher-state/hn.json

Force a replay (next run treated as first poll):

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

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.
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.
Unbounded watermark growth. The shared helper caps at 500 IDs. Raise it for high-churn feeds; lower it on constrained filesystems.
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.