Pass down ToolCall.id to the tool function

[datbth]

Is your feature request related to a problem? Please describe.
I'm displaying a tree of tool calls (i.e. a tool can call its sub-tools or sub-agents), so I need a way for sub-tool calls to refer to their parent tool call.
While there are various ways to generate a UUID and pass it down to tool functions, it is not feasible to persist those IDs into the ChatMessages => It's not feasible to reconstruct the conversation UI from the result ChatMessages.

Imagine a UI that displays:

1. User message
2. Assistant message 1
3. Tool 1
   i. Tool 1a
   ii. Tool 1b
4. Assistant message 2
5. Tool 2

=> Need a way to persist Tool 1a and Tool 1b that can

• Link them to their parent: Tool 1
• Reconstruct the whole conversation (including User message, Assistant message 1, Assistant message 2) in the correct order

Describe the solution you'd like
Either

• Pass down the LLM's tool call id to the tool function
  • As direct argument. Here is my monkey-patch:
  • Or as context variable
• Or provide a way for the tool function to save additional details to the ChatMessage's meta

[tommasocerruti]

I can take this. I would go for approach 1 (pass the LLM tool call id directly) as an optional tool_call_id kwarg, injected only if the tool’s signature accepts it. This keeps the API explicit, avoids hidden global state, and is fully backward-compatible. But before starting to implement it, I'll wait for feedback on this.