Arthur AI

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What is Arthur AI?

• Input: PromptInjectionRule + ToxicityRule
• Output: ToxicityRule

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How it works

1. The gateway POSTs an OpenAI-shaped requestBody (input) or requestBody + responseBody (output) to your wrapper URL.
2. The wrapper extracts user/assistant text and calls Arthur with your ARTHUR_API_KEY.
3. The wrapper returns HTTP 200 with a policy outcome in the body. Infrastructure failures return HTTP 5xx.

TF customer's app ─► TF gateway ─► this wrapper ─► engine.platform.arthur.ai/api/v2/validate

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Response contract

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Wrapper endpoints

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Prerequisites

• Arthur API key from the Arthur platform.
• Public HTTPS URL for the deployed wrapper.
• WRAPPER_API_KEY — shared secret the gateway sends as Authorization: Bearer ….

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Setup

1

Clone and configure

git clone https://github.com/truefoundry/integrations-custom-guardrails
cd integrations-custom-guardrails/integrations/arthur-ai
cp .env.example .env

.env

ARTHUR_API_KEY=<from https://platform.arthur.ai>
WRAPPER_API_KEY=<generate: python -c "import secrets; print(secrets.token_urlsafe(32))">

2

Deploy the wrapper

TrueFoundry:

pip install -U truefoundry
tfy login
python deploy.py --wait

Set TFY_WORKSPACE_FQN, TFY_PUBLIC_HOST, TFY_PUBLIC_PATH, and secret FQNs in .env. Create secrets arthur-api-key and wrapper-api-key under group arthur-guardrails-tfy in Platform → Secrets.Local:

python3 -m venv .venv
.venv/bin/pip install -r requirements-dev.txt
.venv/bin/uvicorn main:app --reload --port 8000

3

Register Custom Guardrail configs

AI Gateway → Guardrails → + Add New Guardrails Group → type Custom.

• Group name: arthur-ai
• Add two configs — input and output.

Input validate example:

Field	Value
Name	arthur-input-validate
Operation	Validate
Target	Request
Enforcing Strategy	Enforce But Ignore On Error
URL	https://<host>/validate-input
Headers	Authorization → Bearer <WRAPPER_API_KEY>; Content-Type → application/json
Config	{}

Output validate:

Field	Value
Name	arthur-output-validate
Operation	Validate
Target	Response
URL	https://<host>/validate-output

Auth Data → Custom Bearer Auth works the same as Headers if you prefer not to set headers manually.

4

Attach to traffic

Model pin: AI Gateway → Models → <model> → Guardrails → attach group arthur-ai.Per request — X-TFY-GUARDRAILS header, selector format <group>/<config-name>:

{
  "llm_input_guardrails": ["arthur-ai/arthur-input-validate"],
  "llm_output_guardrails": ["arthur-ai/arthur-output-validate"]
}

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Custom config (optional)

{
  "checks": [
    {"name": "prompt-injection-check", "type": "PromptInjectionRule", "apply_to_prompt": true, "apply_to_response": false},
    {"name": "toxicity-check", "type": "ToxicityRule", "apply_to_prompt": true, "apply_to_response": false, "config": {"threshold": 0.5}}
  ],
  "fail_closed_on_unavailable": false
}

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Troubleshooting

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Reference