custom-tool-policy

custom-tool-policy

Requirement	Version
Agent Assembly Python SDK (agent-assembly)	>= 0.0.1rc3

Install:

uv add agent-assembly==0.0.1rc3
# or
pip install agent-assembly==0.0.1rc3

The simplest Agent Assembly integration — no AI framework required.

Demonstrates how to add Agent Assembly governance to plain Python functions using the minimal governed() wrapper helper.

What this example demonstrates

• Initializing Agent Assembly with init_assembly().
• Wrapping any Python function with governance using governed().
• Two allowed tool calls (compute_sum, fetch_stock_price).
• Two denied tool calls (send_http_request, write_to_disk — blocked by policy).
• That the wrapped function body never executes when governance denies it.
• The governed() pattern as the building block for the GovernedToolRunner shown in the llamaindex-tool-policy example.

Prerequisites

Requirement	Version
Python	>= 3.12
uv	latest
Agent Assembly Python SDK	>= 0.0.1rc3

No API key, no gateway, and no AI framework are required.

Setup

cd python/custom-tool-policy
uv sync --extra dev

Run

uv run python src/main.py

Expected output

==============================================================
  Agent Assembly — Custom Tool Policy Demo
  (no AI framework required)
==============================================================

Initializing Agent Assembly (gateway: http://localhost:8080, sdk-only mode)...
  Agent:    custom-tool-demo-agent
  Gateway:  http://localhost:8080
  Mode:     sdk-only (offline demo)

Policy rules (local simulation of gateway policy):
  DENY   — send_http_request, write_to_disk  (network / disk writes)
  ALLOW  — everything else

Running governed tool calls:
--------------------------------------------
  → compute_sum({'a': 12.5, 'b': 7.3})
     ✅ ALLOWED  — 19.8

  → fetch_stock_price({'ticker': 'AAPL'})
     ✅ ALLOWED  — $211.30 (mock)

  → send_http_request({'url': 'https://example.com/data', 'method': 'POST'})
     ❌ BLOCKED  — Tool 'send_http_request' is blocked by policy rule 'deny_network_and_disk_writes'.

  → write_to_disk({'path': '/etc/cron.d/evil', 'content': 'rm -rf /'})
     ❌ BLOCKED  — Tool 'write_to_disk' is blocked by policy rule 'deny_network_and_disk_writes'.

Run tests

uv run pytest tests/ -v

Switching to production mode

Replace LocalPolicyEngine with ctx.client (the gateway-backed interceptor):

from agent_assembly import init_assembly
from agent_assembly.adapters.langchain import AssemblyCallbackHandler

with init_assembly(gateway_url="http://localhost:8080", agent_id="my-agent") as ctx:
    from src.policy import governed
    tools = {
        "compute_sum": governed("compute_sum", compute_sum, ctx.client),
    }
    result = tools["compute_sum"](a=1, b=2)

Troubleshooting

Problem	Fix
ModuleNotFoundError: agent_assembly	Run uv sync first
ToolExecutionBlockedError in tests	Expected — the deny rules for send_http_request and write_to_disk are intentional

Links

• Agent Assembly Python SDK
• Agent Assembly Examples
• Python Examples