Saw this earlier but just now getting a chance to respond. Honestly, finding truly free tools inside the GPT store is getting harder since most developers want you to sign up for a trial eventually. If you want to stay within the chat interface, I would check out these two:

• Keyword Insights SEO Keyword Research GPT: This one is excellent for clustering and understanding user intent. The downside is that the volume data is often just an estimate and not real-time.
• Surfer SEO Keyword Research GPT: This is great for generating a topical map and finding long-tail ideas. However, it lacks deep keyword difficulty scores compared to the big paid tools. Basically, use these for brainstorming, but dont expect perfect accuracy for competition metrics without paying a bit. It is kinda the trade-off for staying free.

Honestly, ive been exactly where you are. Starting a niche site on a budget is tough when the big tools like Ahrefs cost a small fortune every month. Since OpenAI moved from the old plugin system to GPTs, finding 100% free, reliable data inside the chat is a bit like finding a needle in a haystack. Most of them eventually ask for a subscription because keyword data is expensive to crawl. In my experience, the best budget-friendly way to do this isnt a single plugin, but a combination. I usually use the Google Keyword Planner Free Tool to grab the actual search volumes first. Its totally free if you have a Google Ads account. Then, I feed that data into ChatGPT to do the heavy lifting of clustering and finding long-tail variations. If you want something more direct, the SEO.app GPT for ChatGPT is decent for content ideas, but for raw data, you might want to look at the Ubersuggest Free Chrome Extension or the Keywords Everywhere Browser Extension. They arent plugins inside the ChatGPT interface, but they provide search volume and difficulty scores directly on your Google search page for free or very cheap. Basically, dont rely on a single magic plugin for everything. Use ChatGPT for the brainstorming and content mapping, but get your raw numbers from the Ahrefs Free Keyword Generator web tool. It lets you check specific keywords without a paid sub and pairs perfectly with ChatGPTs analysis.

Been using this for years, no complaints

Quick reply while I am waiting for a script to finish. I actually went through a phase where I tried to build my own keyword data pipeline using various APIs because I was tired of the massive monthly fees for those big suites. What I learned the hard way is that most GPT-based tools are basically just guessing when it comes to search volume and difficulty scores unless they are pulling from a live database. In my current setup, I found that relying on a single free plugin inside the chat window usually leads to hallucinated numbers. I eventually realized it was better to use the LLM for the semantic mapping and grouping of keywords rather than the raw data itself. I spent way too much time trying to find a shortcut only to realize that the most accurate data usually lives in developer consoles or legacy tools that havent been fully monetized yet. Its a bit of a grind, but it definitely saves a ton of cash.

Like someone mentioned, these GPTs are kinda just guessing most of the time. Its super disappointing because I really wanted them to work for my workflow too, but I had issues with the data being way off compared to real trackers. I totally agree with the others that you gotta be careful about what ChatGPT tells you regarding search volume because it is usually just a hallucination. If you want to look at some other brands that offer at least a little bit for free without a full sub:

• Go with Moz for checking how tough a keyword actually is.
• Just use whatever free daily searches Semrush allows on their web platform.
• Check out SpyFu to see what your competitors are up to. It really is a struggle when you're starting out on a budget but dont let the bad data discourage you. Let me know if you need a hand with anything else!

^ This. Also, qqyohtjqdt is totally right about how some GPTs just guess... it is scary! I once spent weeks on a project because a plugin told me a niche was easy, but it turned out to be a total lie and I wasted so much energy. Honestly, I dont trust most of them now. I am super cautious about where I get my data from!! I have been using the Keyword Surfer Browser Extension lately and it is amazing! It is free and gives you real volume data while you browse, which I then feed into ChatGPT. For long-tail ideas, AnswerThePublic Free Search Tool is also fantastic for finding what folks are actually asking. It is such a relief using stuff that is actually grounded in reality instead of just guessing. Love it!!