ARDGuard

ARDGuard adds an eligibility boundary between agentic resource discovery and final use.

It consumes ranked discovery results, evaluates independently established task-specific capability, evidence, and authority observations, and selects the highest-ranked eligible resource or returns an explicit defer, abstain, or error decision. It never installs or invokes the selected resource.

Status: 0.1.0b4 Beta 3 patch release. The deterministic v1 path remains supported. The extensible v2 kernel and its protocol packs are experimental. See the support matrix before production use.

python -m pip install ardguard==0.1.0b4
ardguard demo

ARDGuard offline demo (illustrative)
rank 1: relevant but capability-ineligible
rank 2: eligible
top-ranked-only validation: ABSTAIN
ARDGuard: SELECT urn:air:example.org:tool:rank-two
reason: selection.fallback_to_lower_ranked_eligible
invocation: NOT PERFORMED

Relevance answers which resource looks useful. Eligibility answers which resource may this agent use for this task.

Put it after discovery

ARD-compatible discovery backend
              |
              v
       ranked candidates
              |
              v
          ARDGuard
  facts + policy + fallback
              |
              v
 SELECT / DEFER / ABSTAIN / ERROR
              |
              v
      caller owns invocation

ARDGuard does not replace ARD, hf-discover, relevance ranking, Sigstore, OAuth, or Kubernetes RBAC. It makes the consumer's final eligibility decision explicit.

JSON in, decision JSON out

Prepare a task contract, policy, and observations, then evaluate any supported ARD SearchResponse:

hf-discover search "read customer records" --json > discovery.json

ardguard evaluate \
  --adapter hf-discover \
  --discovery-response discovery.json \
  --task task.json \
  --policy policy.json \
  --facts facts.json \
  --output decision.json

ardguard explain decision.json

Example decision:

{
  "outcome": "SELECT",
  "reason": "selection.fallback_to_lower_ranked_eligible",
  "selected_candidate_id": "urn:air:example.org:tool:rank-two",
  "selected_rank": 2
}

The actual decision document also contains every candidate verdict, stable reason codes, provider identities, preserved backend scores, and a deterministic body hash.

Python integration

from ardguard import FactSet, Policy, TaskContract, evaluate
from ardguard.adapters import parse_search_response

candidates = parse_search_response(discovery_response)
decision = evaluate(
    candidates=candidates,
    task=TaskContract.from_mapping(task_document),
    policy=Policy.from_mapping(policy_document),
    facts=FactSet.from_mapping(fact_document),
)

if decision.outcome.value == "SELECT":
    # The caller may now decide whether and how to invoke the resource.
    print(decision.selected_candidate_id)

Why fallback matters

A top-ranked-only validator can reject an ineligible first result, but it also abandons the task when a lower-ranked candidate is eligible. ARDGuard evaluates the configured candidate set, preserves the backend's rank among eligible candidates, and returns the highest-ranked eligible candidate. It does not manufacture or reinterpret relevance scores.

Contracts, not self-asserted eligibility

Public callers supply observations, not eligible: true. ARDGuard derives candidate verdicts from versioned contracts:

• TaskContract states required operations, evidence, and authority limits.
• FactSet binds typed observations to candidate and provider identities.
• Policy controls required checks, uncertainty, and fallback.
• Decision reports SELECT, DEFER, ABSTAIN, or ERROR with stable reasons.

Missing facts, unavailable verifiers, and operational errors fail closed. An operational verifier failure is never reported as an invalid signature. Authentic evidence for artifact A never makes candidate B eligible.

Commands

Extensible kernel

Beta 3 includes an experimental v2 kernel for third-party fact types, typed requirements, decision receipts, stdin/stdout integration, and a loopback HTTP API. Beta 2 v1 contracts remain unchanged. Start with the existing commands above; advanced integrators can read the extensibility guide and eligibility-pack matrix.

Documentation

• Five-minute integration guide
• Architecture
• Security model
• Supported scope
• Decision and reason codes
• Fact providers
• Extensible kernel
• Eligibility packs
• ARD v0.91 compatibility
• hf-discover integration
• Evidence
• Authority policy

Examples

• Basic capability decision
• Rank-preserving fallback
• Authentic but non-applicable evidence
• Authority-aware fallback
• ARD v0.91 SearchResponse
• Pinned hf-discover response

Development

python3.12 -m venv .venv
.venv/bin/pip install -e '.[dev]'
.venv/bin/pytest
.venv/bin/ruff check .
.venv/bin/mypy src/ardguard

Small compatibility fixtures, provider implementations, reason-code improvements, and reproducible interoperability reports are welcome. Read CONTRIBUTING.md and SECURITY.md first.

License

Apache License 2.0. See LICENSE and NOTICE.