Struct ConcurrencyPermit 

pub struct ConcurrencyPermit { /* private fields */ }

Core traits and types.

Always available regardless of feature flags. Includes:

• Agent - The fundamental trait for all agents
• Tool / Toolset - For extending agents with capabilities
• Session / State - For managing conversation context
• Event - For streaming agent responses
• AdkError / Result - Unified error handling RAII guard that releases semaphore permits on drop.

A ConcurrencyPermit holds at most one global permit and one per-tool permit. When the permit is dropped, the underlying semaphore slots are released, allowing queued tool calls to proceed.

Example

use adk_core::{ToolConcurrencyConfig, ToolConcurrencyManager};

let config = ToolConcurrencyConfig {
    max_concurrency: Some(3),
    ..Default::default()
};
let manager = ToolConcurrencyManager::new(&config);

let permit = manager.acquire("my_tool").await.unwrap();
// Tool executes while permit is held...
drop(permit); // Semaphore slot released