Because LLMs such as Gemini -- and other causal language models more broadly -- are trained on next token prediction, the vectors that you get from pooling the

Because LLMs such as Gemini -- and other causal language models more broadly -- are trained on next token prediction, the vectors that you get from pooling the output token embeddings aren't that useful for RAG or semantic search compared to what you get from actual embedding models. One distinction to make here is that token embeddings and the embeddings/vectors that are output from embedding models are related but separate concepts. There are numerous token embeddings (one per token) which become contextualized as they propagate through the transformer, while there is a single vector/embedding that is output by embedding models (one per input data, such as long text, photo, or document screenshot).