Function call_tool 

pub async fn call_tool<Ctx: Send + Sync + 'static>(
    tool: Arc<dyn ToolFunction<Ctx>>,
    tool_args: Value,
    tool_context: Arc<ToolExecutionContext<Ctx>>,
) -> Result<ToolResult, AgentError>

Validate tool arguments against its JSON schema and then execute it.

This is the canonical entry-point for invoking a ToolFunction from the agent runtime. It first checks schema conformance with jsonschema, then calls ToolFunction::execute.