YES, you need to be transparent. This is a policy that is common to all Stack Exchange sites. Quoting the help center:
Avoid overt self-promotion.
The community tends to vote down overt self-promotion and flag it as spam. Post good, relevant answers, and if some (but not all) happen to be about your product or website, that’s okay. However, you must disclose your affiliation in your answers.
If a large percentage of your posts include a mention of your product or website, you're probably here for the wrong reasons.
As this site is more prone than most to potential spam, astroturfing and other excessive promotion, our stance on self-promotion has to be especially strict. Quoting the ground rules:
Answering recommendation questions
(…) Answers that contain little more than a link will be deleted without question, comment or other ceremony. Additionally, our policy on excessive self-promotion will be even more heavily enforced on the site. If you're asked to stop promoting a product that you're affiliated with by a moderator or community manager - you need to stop, or you'll likely be asked to leave the site. Spam filters will be adjusted accordingly - so be careful.
If you work on a product, be it free, gratis or proprietary - it's fine to recommend it to people opportunistically provided that you include full disclosure of your involvement with the product. If more than a small percentage of your posts mentions your product, we're probably going to need to have a talk.
Good answers on this site will be in the form of honest testimonials that share first hand experience with something and why it meets the needs of the asker.