AI Tools Every Developer Should Know in 2025

Here is what members of AI Underground are actually using across our global community.

For Building AI Applications

• Vapi.ai - Fastest path to a working voice agent, handles the entire STT, LLM, and TTS stack
• Instructor - Structured outputs from LLMs every time
• LangChain and LlamaIndex - Still useful for complex pipelines
• DSPy - Best for serious prompt optimisation at scale

For Vector Storage

• pgvector - If you are already on Postgres, start here
• Qdrant - Best performance for high-scale vector search
• Weaviate - Good hybrid search out of the box

For Observability

• Langfuse - Open source LLM observability with cost tracking
• RAGAS - Automated evaluation for RAG pipelines

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