What an indicator cannot see
The boundary of the tool, stated plainly. Knowing what is outside it is more useful than another setting.
An indicator reads what the data feed gives it: open, high, low, close, volume, and time. Everything else is outside the boundary. The list below is not exhaustive, but it covers the gaps that cost people money.
Who is transacting, and why
A large sell can be a fund reducing risk, a hedge against an unrelated position, an index rebalance, or a forced liquidation. The chart records the same downward bar in each case, and the implications are entirely different. No amount of processing recovers the reason.
The order book
Standard chart data records completed trades. Resting orders, size sitting at a level, orders pulled the instant price approaches — none of that reaches an indicator computing from bars. Depth-of-market tools address this and are a different category with their own limits.
Anything scheduled
An economic release, an earnings date, an expiry, a rollover, a central bank decision. The chart does not know Wednesday is different from Tuesday. Conditions before a major release are not comparable to ordinary conditions, and every measure on your screen will treat them identically.
The wider market
Unless it is explicitly fed other instruments, an indicator on one chart sees one instrument. It cannot know the whole sector is moving, that a correlated contract broke first, or that a broad index is driving everything on the screen.
Liquidity conditions
The same setup in an active session and in a thin holiday market is not the same setup. Volume gives a partial view. Spread, market depth, and slippage do not appear in bar data at all.
Your situation
This is the one that matters most, and it is worth being blunt about. An indicator does not know your account size, your position, your other exposure, your tax situation, your timeframe, what you can tolerate losing, or what happened to you last week.
This is the specific reason a mark on a chart is not advice, and it is not a legal formality. The tool has no access to the information that would be required to make a recommendation. It is answering a narrow question about price history. You supply everything else.
What to do with this
Treat the boundary as part of your process rather than a disclaimer to scroll past. Before acting on any chart-based observation, check the things the chart cannot see: what is scheduled today, what the related markets are doing, whether the session is normal, and what the position means for your account specifically.
That check takes under a minute and it addresses the failure modes no setting can.