Which one is an antonym of 'Mendacious'?

Mendacious (adjective)
English Meaning: Not telling the truth; lying.
Bangla Meaning: (আনুষ্ঠানিক) মিথ্যা; মিথ্যাবাদী: mendacious reports.

Synonyms: Untruthful (মিথ্যাবাদী), Dishonest (অসাধু), Deceitful (প্রতারণাপূর্ণ).
Antonyms: Truthful (সত্যনিষ্ঠ).

Other Forms:
- Mendaciously (adverb)
- Mendacity (noun) (আনুষ্ঠানিক) [uncountable noun] মিথ্যা; [countable noun] (plural mendacities) অসত্য বিবরণ।

Example Sentence: ‘That promise has been revealed as mendacious nonsense.’

Source: Website Lecture.