Had anyone noticed that the scriptures don’t explicitly tell mantras to be chanted?

I was reading a scripture, I forgot which, and it tells that they should chant a specific mantra for Shiva. They don’t give it explicitly though. They describe it and we have to reconstruct the mantra. For example they may say “na” is the third syllable and “ma” is the fourth syllable, and such. Sometimes they say that the mantras is bits and pieces of other mantras. How come they don’t just directly tell the mantra, instead of describing it.