Everytime I play agar.io I see a lot of users playing with bots and they get big really fast. Honestly, I hate those bots. But I'll show you below how to do the same, even at no cost (cuz they pay for each bot).
If you'd like o play agar.io with 500 bots for 24 hours, you need to pay up to $30 if you buy bots from v-cells.co - but hows shoud to get those bots absolutely free? I bet you'll love them.
www.agariohack.online is a website which can generate for you up to 500 bots with no cost, so you don't need to pay a penny. One of the problem is that you can play only once. Everytime you want to play with agar.io bots, you need to generate a new code on that generator.
Check out that website, generate bots and enjoy. You can also generate up to 100k coins, speed, mass boost, invisibility and other such amazing features.