I use my own notation for dynamic fields like that, and have my agents system prompt have it's fields replaced at the time of the call being created. Not only does this help for things like current data, but also when I want other data to be swapped out in the system prompt. Such as a leads first name and company. I have much more control this way but also can have highly dynamic system prompts. For example "role play as a helpful assistant. You are speaking to presumably John from JJ plumbing and the current time is 02:45pm 12/12/2024. "