ARIA MCP Gateway

How it works

1. Validate ARIA Passport and session.
2. Check policy for requested tool and operation.
3. Enforce constraints and obligations; call tool.
4. Write a signed, hash‑chained receipt.

Guardrails at the edge

Gateway enforces the PDP's guardrails where calls enter: scope and parameter allow‑lists, egress rules, anti‑injection checks, and budget stops. Safe by default, fast in practice.

Plan JWS (per step)

{
  "step": 3,
  "tool": "billing.export",
  "params_fingerprint": "sha256-...",
  "schema_hash": "sha256-...",
  "iat": 1738020000
}

Gateway verifies the JWS signature and payload fields to ensure the call matches the planned step.

Schema pins & allowlists

{
  "schema": { "id": "billing.export", "version": "2.3.1", "hash": "sha256-..." },
  "params_allow": ["account_id", "month"],
  "egress_allow": ["https://api.example.com"]
}

Pins prevent drift; parameters and egress are enforced at the boundary with PDP constraints.

Budget control: pre‑gate + settle

The PDP checks live budgets before a call (no tokens spent). For streams, Shield reserves a cap and truncates output the instant the budget boundary is reached.