Caution on yoga lists in online tools
Yogas are rules from classical texts, and a yoga present in a chart is not a prediction. It shows that a combination's rule is met, and the classical reading of that combination is one part of the whole chart.
What it is
Many yogas appear in a typical chart, and the texts disagree on several of them. Reading one yoga in isolation can give a misleading picture, which is why the whole chart and the dashas are read together.
How it is worked out or read
The site lists the result of each checked yoga, and does not give a combined verdict. If you rely on a yoga result, check its rule and its cancellations in the source.
Where it appears on this site
The checked yogas are in the birth chart. The accuracy checklist lists what to check first.
Why yogas need special care
Yogas are among the most attractive parts of Jyotish for beginners, because each one comes with a vivid name and a clear promise. That same vividness makes them easy to misuse. A yoga noticed without its conditions can make a reading sound far more certain, or far more alarming, than the chart justifies.
Check the definition
Many yogas have more than one definition. Gajakesari, for example, is defined in some texts as Jupiter in a kendra from the Moon, and in others with further conditions about Jupiter's strength and aspects. Kemadruma is defined differently by different authors, and its cancellation rules vary. Before relying on a yoga, find out which definition is being used and from which text.
Check the strength
A yoga formed by weak planets gives weak results, according to the texts themselves. Debilitation, combustion, placement in the sixth, eighth or twelfth house, and affliction by malefics all reduce a yoga's effect. A Raja yoga between a debilitated ninth lord and a combust tenth lord is not the same as one between strong planets in good houses, though both carry the same name.
Check the timing
Yogas are said to show their results chiefly in the dashas of the planets that form them. A yoga whose planets' periods fall in childhood or late old age may have little visible effect in the person's working life. Looking at the dasha sequence alongside the yoga list gives a more realistic picture.
Keep the whole chart in view
The most important caution is not to let a single yoga define a chart. Every chart contains supportive and difficult features, and the texts expect a reader to weigh them together. The yoga check on this site lists nine standard yogas as present or absent with the rule for each, and states that it does not apply cancellations; it is a starting point for study, not a verdict.
A habit worth forming
Whenever you note a yoga, write next to it the definition used, the strength of its planets and the dashas in which it may act. The habit takes a minute and prevents most misreadings.