Fast answer
Trendline signals need anchor points and a rule for failure.
Before using a trendline crypto signal, check the original line placement, anchor points, chart time frame, breakout or rejection rule, retest condition, invalidation, stop plan, target logic, update trail, and final status. A line drawn after the move is not enough.
If the line appears only after price already moved, ask for the original timestamped chart and the invalidation rule.
Line checks
What to inspect in a trendline signal.
Anchor points
Check the two or more points used to draw the line and whether wicks, closes, or zones are being used consistently.
Time frame
A trendline on a short chart can break many times. The signal needs the chart interval and the expected holding period.
Trigger rule
Record whether the call uses a break, close, retest, rejection, fakeout filter, or confirmation candle.
Update trail
The provider should preserve redraws, cancelled setups, stop movement, target changes, and final close status.
Source context
Trendlines are manually placed chart tools.
TradingView's trendline drawing tool help page describes the tool as a way to manually draw lines that illustrate trends or points of interest. Because line placement is manual, source charts and timestamps matter when reviewing a provider's signal.
Review standard
Trendline calls should show before-and-after evidence.
A reviewable trendline signal includes the original chart, anchor points, time frame, trigger rule, entry, invalidation, stop, target, updates, redraws, and final status. After-the-fact line drawings should not be treated as track-record proof.