You are looking for proof that your words and your charm were handed to you for free. The proof exists. It is filed somewhere else.
What it looks like in a life
Both planets orbit closer to the Sun than Earth does, so they never spread far enough apart to make a trine. What you are probably reading is Mercury conjunct Venus, which fuses thought and taste into one motion, or the two sitting in neighbouring signs of the same element. Easy speech also comes from Mercury trine Jupiter, Mercury trine the Moon, or Venus trine Neptune.
The gift
Knowing the geometry keeps you honest about where your ease actually comes from.
The friction
If a chart report lists Mercury trine Venus, it is a software error or an orb set far too wide. Treat the rest of that report with the same suspicion.
The esoteric layer
Trines were defined as a third of the circle, signs sharing an element, and Hellenistic astrologers built that on the geometry of the sky. The sky does not put Mercury and Venus a third of a circle apart.
Where this goes
The trines you do have are unearned capital, and they are meant to be spent. A full natal reading finds them and says what they are for.
Related
See it in your own chart
Cast your chart free and read this placement next to everything else you carry.