I wanted to grow my LinkedIn reach. Engaging with posts and leaving comments are both easy on their own. Doing both every day, without losing patience, is the part that breaks the routine. So I searched for a tool that could hold the line for me.
Every Comment Tool I Tested Rate-Limited Me Into a $250 Plan
I found a wasteland of $49-a-month "basic" plans that cap you at 20 comments a day. Other tools charged $17 a month and stayed just as restrictive. The $49 plan works out to $1.63 a day for 20 comments. I did the math. The math made me sad.
I tested every one of them anyway. Some promised huge results. Some ran sleek landing pages with testimonials from "Sarah K., Marketing Director."
Seven-day trials pushed me toward a subscription before day eight. Freemium plans turned out to be paid plans with a free preview attached. Rate limits got so strict that typing the comment myself beat waiting on the tool. I was one click from a $250 annual plan when I stopped and looked for one more option.
Butterfly Runs on Your Own Free Gemini Key, Not a Subscription
Butterfly is a Chrome extension with four ratings, and four is the real count, not a rounding trick. Four ratings does not prove much on its own. I read the code on the extension's GitHub repo before I handed it a Gemini key, because the repo sits in the open for anyone to check.
GitHub: Butterfly Repository Chrome Store: Install Extension
It's a simple extension that runs on your own free Gemini API key instead of paying a SaaS platform's monthly rent.
The setup takes about two minutes.
Install the extension.
Grab a free Gemini API key from Google.
Paste the key into the extension.
Write your own prompt.
Start commenting.
Butterfly writes in your own voice, because you supply that prompt instead of a canned one. You set the tone and the length, and you decide whether a comment ends in a question. Per its own GitHub README, it works on LinkedIn, on X, and on Product Hunt. There is no monthly subscription, no upgrade popup, no invented five-comment cap, and no card to put on file.
Google's free tier funds the whole thing. Gemini 2.5 Flash gives you 20 requests a day. Gemini 2.5 Flash-Lite gives you 1,000 requests a day, according to Google's own Gemini API rate-limits documentation. Gemini 3.0 Flash in preview is available too. Switch models when one runs dry, because each model carries its own separate quota.
The Only Limit Left Is Google's Rate Limit, Not Butterfly's
The only cap on Butterfly is whatever the Gemini free tier allows that day. Paid tools charge from $17 a month up to $250 a year for the same function and hand you a tighter limit than Google gives away for free.
I spent three hours on this search, tested tools that failed at the first paywall, and nearly gave up before I found this one. Those $250-a-year tools most likely call the same Gemini API underneath. You pay them to sit in the middle of a connection you can build yourself for free.
The Free Extension Beat the $250 Plan
The best tool is not always the one with the biggest marketing budget. This time it was a small extension with four Chrome reviews. Skip Butterfly only if a paid tool you already own is actually earning its subscription fee.
Thank you to the developer. You saved me $250 and hours of testing dead tools.
Drop a comment. I will probably auto-respond to it with this exact extension.
Related reading: The MrBeast Blueprint: YouTube Growth Tactics and How to Get Your First 10,000 Users Without Spam.
The pricing economics here are eye-opening. Any data privacy tradeoffs using your own key.
Here's the TL;DR version of this:
• Most LinkedIn engagement tools resell free APIs with markup.
• Pricing is disconnected from actual technical value delivered.
• Butterfly runs entirely on your own Gemini API key.
• This removes subscriptions while keeping full prompt control.
• The best tools often have the least marketing.