haystack-tool-policy

haystack-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

Demonstrates Agent Assembly governance over a real Haystack agent using the SDK's native Haystack adapter.

Haystack has a native adapter: HaystackPatch hooks haystack.tools.Tool.invoke — the single execution chokepoint Haystack 2.x uses for every tool, including the agentic Agent → ToolInvoker tool-call loop. This example governs three real haystack.tools.Tool instances by driving them through a genuine ToolInvoker (the component a Haystack Agent uses to execute a model-chosen tool call), so a denied tool is short-circuited before its body runs — real governance, not a no-op.

What this example demonstrates

• Initializing Agent Assembly with init_assembly() (which auto-detects Haystack).
• Installing the native Haystack adapter (HaystackPatch) against a local policy.
• Running real haystack.tools.Tool calls through a real ToolInvoker.
• An allowed tool call (query_index) — the tool body executes.
• Another allowed tool call (summarize_docs).
• A denied tool call (execute_sql — blocked by deny_arbitrary_execution); its underlying function never runs.

Prerequisites

Requirement	Version
Python	>= 3.12
uv	latest
Agent Assembly Python SDK	>= 0.0.1rc3
Haystack	>= 2.0.0, < 3.0

No API key or running gateway is required for the offline demo — the tools are driven through a ToolInvoker with a hand-built ToolCall, so no LLM is involved.

Setup

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

Run

uv run python src/main.py

Expected output

==============================================================
  Agent Assembly — Haystack Tool Policy Demo
==============================================================

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

Policy rules (local simulation of gateway policy):
  DENY   — execute_sql, run_shell_command  (arbitrary execution)
  ALLOW  — everything else

Installing the native Haystack adapter against the demo policy...
  Adapter installed: True

Running real Haystack tools through a ToolInvoker:
--------------------------------------------
  → query_index({'query': 'what is Agent Assembly?'})
     ✅ ALLOWED  — Index results for 'what is Agent Assembly?': [chunk-12, chunk-44, chunk-07] (mock)

  → summarize_docs({'topic': 'policy enforcement'})
     ✅ ALLOWED  — Summary for 'policy enforcement': Agent Assembly provides governance... (mock)

  → execute_sql({'sql': 'DROP TABLE users; --'})
     ❌ BLOCKED  — [BLOCKED by governance policy] Tool 'execute_sql' is blocked by policy rule 'deny_arbitrary_execution'...

Tool bodies that actually executed: ['query_index', 'summarize_docs']

execute_sql is absent from the executed list — the deny short-circuited it before the tool ran.

Run tests

uv run pytest tests/ -v

How the offline demo wires the policy

init_assembly() auto-detects Haystack and patches Tool.invoke for you. In offline sdk-only mode it wires a no-op interceptor (there is no live gateway to answer policy), so this demo reverts that and re-installs the same native adapter against a LocalPolicyEngine to make a real allow/deny visible without a gateway.

In production you point init_assembly() at a gateway and let its auto-detected adapter enforce real policy — no manual re-install needed:

with init_assembly(gateway_url="https://your-workspace", api_key="...", agent_id="my-agent") as ctx:
    # Haystack tools are governed automatically from here.
    ...

Troubleshooting

Problem	Fix
ModuleNotFoundError: agent_assembly	Run uv sync first
ModuleNotFoundError: haystack	Run uv sync — haystack-ai is a required dependency
execute_sql shows ALLOWED	Make sure the demo policy is installed after init_assembly() (it reverts the auto-applied no-op patch); see src/main.py

Links

• Agent Assembly Python SDK
• Haystack docs
• Agent Assembly Examples
• Python Examples