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// Honest AI tool & model comparisons

I test which AI answers you can trust, where being wrong costs real money.

One email a week: which AI answers held up, which fell apart, and the prompts I’d run again.

Get the free Field Guide → ~20 pages, instant, no email needed.
// The Lessons20 documented failures // Latest test:
  1. ChatGPT·misattributed-source

    Asked for the UK ISA partial-transfer rule with a source, ChatGPT (free, web search on) cited…

  2. Perplexity·low-authority-source-led

    Asked how long cooked chicken keeps in the fridge by a stated UK (Newcastle) user, Perplexity (web search on) led with US food…

  3. Perplexity·outdated-rule-stated-as-current

    Asked whether this year's ISA contributions can be partially transferred, Perplexity said they must be transferred in full, the…

All evidence
Ben Dixon
// The author

I started testing AI because I wanted to know which tools could be trusted with a real decision: my own investing first, where a wrong answer comes with a bill. The verdicts here are what I found, including the times a tool simply wasn’t worth paying for. More on why I do this →

20 AI errors logged 15 AI catches 14 trades documented May 2026 tracking since
// New here? Start here. 4 parts · ~14 min · no jargon

A short, plain-English path to trusting what AI tells you.

Four short reads. By the end you’ll have a simple check you can run on any answer that matters: a contract, a letter from a doctor, an email you’re not sure about.

Start with part 1 →
  1. 01 How to tell if an AI answer is true in 30 seconds
  2. 02 The whole method, in four questions
  3. 03 Make it show its working
  4. 04 Where I actually use this
// See all four parts →
// From the field · 9 new this week
Field Notes

AI stock picker: I asked three models if I should buy NVDA, and watched the methodology break

I asked three AI models whether to buy NVDA. Same confident tone from all three, and only one volunteered which of its own numbers not to trust yet.

New · · 12 min read
Field Notes

Does ChatGPT make up sources? I checked two finance claims against the actual pages

Does ChatGPT make up sources? Mostly no, but I opened every link on two finance questions and found a real gov.uk page that didn't back the claim.

New · · 11 min read
Field Notes

Does web search make AI more accurate? I ran the same questions both ways

Does web search make AI more accurate? I ran the same questions both ways. It didn't make the answers more reliable. It moved where the errors hide.

New · · 10 min read
// Archive
Field Notes AI ISA advice: I tested four tools on the questions people get wrong New · 12 min Field Notes I asked 4 AIs to scale a recipe. Two got the maths wrong. New · 9 min Field Notes 9 types of AI hallucinations, named from real tests New · 17 min Tool Audit AI stock research tools tested: what each one got wrong New · 14 min Tool Audit ChatGPT vs Claude for earnings call analysis: which one reads what management didn't say New · 13 min Tool Audit Is Perplexity good for investment research? An honest, scored audit New · 14 min
Browse all →
// By topic Prompt StackTool AuditDecision ProcessField Notes

// The Method Four prompts that stop AI inventing the answer.

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