Comment by Phemist

If an agent makes a tool call, the LLM provider will receive the full context again after the result of the tool call becomes available in order to decide the next move. Everything up to the point of the tool call being made will no longer change and could thus in theory be cached. If the agent makes a ton of tool calls, then for every tool call one should be hitting the cache an equal amount of times.

A new instruction by the user will be appended at the end if it done in the same conversation. Thus only has influence on the cacheability of the original agent prompt, but not of subsequent tool calls.