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Side-by-side: what they do, what they cost, what Kai actually thinks. Pass up to 4 tools via ?tools=claude,chatgpt,gemini.
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DeepSeek
S
Lex
A
Claude Agent SDK
S
Perplexity
S
TaglineChinese open-weight powerhouse. Crazy cheap, genuinely smart.Google Docs with an AI collaborator baked in.Anthropic's SDK for building your own agents on Claude.AI search done right. Cited answers, not chat theater.
CategoryChatbotsWritingAgentsResearch
PricingFree web + ultra-cheap API (~$0.14/M input tokens)Free + $12/moAPI usage + SDK is freeFree + $20/mo Pro
Best forDevelopers + cost-conscious builders. Anyone fine with self-hosting.Essays, long-form drafts, thinking on the page.Developers building custom agents for their own company/product.Replacing Google for any question where you want a cited answer in seconds.
Strengths
  • Open weights you can self-host
  • Strong reasoning + math
  • Near-free API pricing
  • DeepSeek-V3 / R1 are serious models
  • Clean writing UX — distraction-free
  • +++ prompt triggers AI help
  • Collaboration + AI feedback together
  • Production-grade agent primitives
  • Built on Claude (best reasoning)
  • Full control — build exactly what you need
  • Sources every claim
  • Fast, current answers
  • Pro Search runs multi-step research
  • Spaces for persistent context
Weaknesses
  • Data goes to servers in China — privacy concerns for business use
  • Chinese policy filters
  • English polish trails Western models
  • Less feature-rich than Google Docs
  • AI ceiling below dedicated tools
  • Developer-only
  • You build the UI
  • Not a general chatbot
  • Answers can be shallow on complex topics
Kai's verdictS-tier for price/performance. A-tier for consumer use. If you build apps, this is the budget pick.A-tier. Beautiful UX. The writing app I'd pick if I only wrote long-form.S-tier for builders. The right primitives. What Kai is built on under the hood.S-tier for search. I use it before Google now. If you're still Googling everything, try this for a week.
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