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In agentic workflows, tools can fail due to rate limits, network glitches, or temporary API downtime. Instead of the agent giving up or asking the user for help, a post-hook allows the system to:
  • Intercept the failed tool response.
  • Analyze the error (e.g., checking for a 429 or 500 status code).
  • Trigger a retry autonomously, ensuring a seamless user experience. 
"""
Retry Tool Call From Post Hook
=============================

Demonstrates retry tool call from post hook.
"""

from agno.agent import Agent
from agno.db.sqlite import SqliteDb
from agno.exceptions import RetryAgentRun
from agno.models.openai import OpenAIChat
from agno.run import RunContext
from agno.tools import FunctionCall, tool
from agno.utils.log import logger

# ---------------------------------------------------------------------------
# Create Agent
# ---------------------------------------------------------------------------


def post_hook(run_context: RunContext, fc: FunctionCall):
    logger.info(f"Post-hook: {fc.function.name}")
    logger.info(f"Arguments: {fc.arguments}")

    if run_context.session_state is None:
        run_context.session_state = {}

    shopping_list = (
        run_context.session_state.get("shopping_list", [])
        if run_context.session_state
        else []
    )
    if len(shopping_list) < 3:
        raise RetryAgentRun(
            f"Shopping list is: {shopping_list}. Minimum 3 items in the shopping list. "
            + f"Add {3 - len(shopping_list)} more items."
        )


@tool(post_hook=post_hook)
def add_item(run_context: RunContext, item: str) -> str:
    """Add an item to the shopping list."""
    if run_context.session_state is None:
        run_context.session_state = {}

    if "shopping_list" not in run_context.session_state:
        run_context.session_state["shopping_list"] = []

    run_context.session_state["shopping_list"].append(item)
    return f"The shopping list is now {run_context.session_state['shopping_list']}"


agent = Agent(
    model=OpenAIChat(id="gpt-5.2"),
    session_id="retry_tool_call_from_post_hook_session",
    db=SqliteDb(
        session_table="retry_tool_call_from_post_hook_session",
        db_file="tmp/retry_tool_call_from_post_hook.db",
    ),
    # Initialize the session state with empty shopping list
    session_state={"shopping_list": []},
    tools=[add_item],
    markdown=True,
)

# ---------------------------------------------------------------------------
# Run Agent
# ---------------------------------------------------------------------------
if __name__ == "__main__":
    agent.print_response("Add milk", stream=True)
    print(
        f"Final session state: {agent.get_session_state(session_id='retry_tool_call_from_post_hook_session')}"
    )

​
Run the Example

# Clone and setup repo
git clone https://github.com/agno-agi/agno.git
cd agno/cookbook/91_tools/exceptions

# Create and activate virtual environment
./scripts/demo_setup.sh
source .venvs/demo/bin/activate

python retry_tool_call_from_post_hook.py
For details, see Post hook tool retries cookbook.