System Prompt Size · AI Accelerator

System Prompt Size

I have developed an appointment booking and general practice questions answerer in n8n (via Telegram and Email) and also made available on ElevenLabs.

I started with a moderate sized system prompt which I evolved to address issues as they came and also added examples.

I eventually ended up with a system prompt of size 25 KB.

I noticed that only the top level LLMs, particularly Gemini 2.5 Flash were able to accurately handle the system prompt effectively and follow instructions.

My question is how large a system model can practically grow? Is things like 25 KB too large? Is it better to reduce the system prompt size may be by removing the examples?

Generally, scheduling scenarios are complex and I noticed I needed to address many cases, but now I feel only Gemini 2.5 Flash and GPT 4.1 are only capable of following on.

Regards

Shadi Ghaith

2 comments

System Prompt Size