Pre-market watchlist briefing in Slack

Build me a pre-market watchlist briefing as an agent workflow. It should run on a cron every US trading weekday (Monday through Friday) at 8:30am ET.

Step 1. Read my watchlist tickers from Google Sheets using the Get Values operation. The tickers live in a single column of a sheet I will configure on the workflow (spreadsheet ID, sheet/tab name, and A1 range). Parse the column into a clean list of ticker strings and trim whitespace. Skip blank rows.

Step 2. For each ticker, call YCharts using the Get Company Data Points operation to pull: current price, prior close, 1-day percent change, P/E ratio, market cap, 52-week high, and 52-week low. Batch the symbols into a single YCharts call where possible (YCharts allows up to 100 symbols per request). If YCharts returns an error for a specific ticker (per-symbol meta.status of "error" or a missing result), skip that ticker and continue. Do not fail the whole run because one symbol is bad. Keep a short list of the skipped tickers so you can mention them at the end of the briefing.

Step 3. Write a short narrative briefing (roughly 150 to 300 words). It should:

• Lead with the biggest movers (top gainers and top decliners by 1-day percent change). Name the tickers, the price, and the percent move.

• Call out any tickers trading near a 52-week extreme (within roughly 3 percent of the 52-week high or low). Say which extreme and how close.

• Flag any unusual valuation signals (for example, a P/E that looks unusually high or low for the watchlist, or a notable market cap shift). Keep this short and qualitative.

• End with a one-line note listing any tickers that were skipped because YCharts did not return data, if there were any.

Step 4. Post the briefing to a Slack channel using the Send a Message operation. The target channel is a workflow setting. Format the message using Slack mrkdwn (not standard Markdown), which means:

• Use *single asterisks* for bold around ticker symbols, section headings, and the most important numbers.

• Use _underscores_ for italics sparingly.

• Lead with a date-stamped headline like *Pre-market watchlist — Mon May 29*.

• Use short sections (Movers, Near 52-week extremes, Valuation flags) so the post is scannable on mobile.

• Prices should be formatted with a dollar sign and two decimals. Percent moves should include a sign and a percent symbol (for example, +2.4% or -1.1%). Market cap should be human-readable (for example, $2.1T or $48.6B).

Error handling and run safety:

• If the Google Sheet read fails or returns zero tickers, post a one-line Slack message saying the watchlist could not be loaded and stop. Do not silently no-op.

• If YCharts is fully down (all symbols error or the call itself fails), post a one-line Slack message saying market data is unavailable and stop.

• Otherwise always post the briefing, even if some tickers were skipped.

Configurable settings I want exposed on the workflow: the Google Sheet (spreadsheet ID, sheet/tab name, A1 range for the ticker column), the Slack channel to post to, and the schedule (default 8:30am ET, Monday through Friday). Keep the agent instructions clear so I can later edit the tone of the briefing or what counts as a notable mover.