Boundra · Payment approval gateway for AI agents

Boundra (boundra.io) — Boundaries for agent payments. The boundary layer for agent payments: before any money moves, answer "should this payment happen at all?"

Our thesis: the opportunity in agent payments is not "how to pay" (protocols solved that) but "whether to pay."

One natural-language rule → compiled into a policy → every payment the agent attempts is genuinely evaluated → allow / ask a human / veto, with a full audit trail.

Two run modes:

• Offline simulation (demo.py): stdlib only, self-contained mock merchant and wallets, zero dependencies, zero network

• Real protocol (demo/demo_real.py): standard MCP server + real x402 SDK + Base Sepolia testnet

Data flow

Policies and keys stay with the user; the gateway is read-only; only hash commitments go on-chain. Revocation is free — forever, no exceptions.

Related MCP server: Cerberus

See it run in 60 seconds

# 1. Hit the hosted evaluation API — a real, public x402 merchant
curl -X POST https://api.boundra.io/evaluate/basic \
  -H 'Content-Type: application/json' \
  -d '{"intent":{"amount":0.01,"recipient":"api.weather.com","purpose":"weather data"}}'
# → {"decision":"ALLOW",...}  ·  semantic layer: 100 free calls per agent, then $0.003 via x402

# 2. Local end-to-end simulation — a data-procurement agent's day
.venv/bin/python demo/simulate_agent.py
# signed policy publish → ALLOW / DENY (limit) / ASK → user-signed approval token
# → prompt-injection blocked → audit trail, plus a dogfood call to api.boundra.io

# 3. One-line MCP install + 2-minute policy wizard
uvx --from git+https://github.com/gobeyondfj-cmd/boundra boundra-mcp     # stdio server
uvx --from git+https://github.com/gobeyondfj-cmd/boundra boundra-init    # wallet → template → sign → anchor
uvx --from git+https://github.com/gobeyondfj-cmd/boundra boundra-approve # sign an ASK challenge

The complete flow, step by step

Zero to a signed, enforced policy in ~10 minutes. No accounts, no dashboards — your wallet key is your identity.

0 · Try the hosted API (30 seconds, nothing to install)

curl -X POST https://api.boundra.io/evaluate/basic \
  -H 'Content-Type: application/json' \
  -d '{"intent":{"amount":0.01,"recipient":"api.weather.com","purpose":"weather data"}}'

1 · Bind your identity — the wallet is the account

uvx --from git+https://github.com/gobeyondfj-cmd/boundra boundra-init

Creates or imports a Base wallet. No signup, no email — the private key never leaves your device, and your address is your identity everywhere in the system.

2 · Set your policy

The wizard offers templates (personal assistant / travel / dev API / procurement) or lets you write your own rule in plain English, then compiles it and shows you exactly what will be enforced — before anything is signed.

3 · Sign & publish

You sign the policy document with your wallet key (EIP-191). It is published as a versioned document and a hash commitment is anchored on-chain. From this moment the gateway is read-only for every agent — changing the policy without your key is impossible.

4 · Mount the MCP server into your agent

{ "mcpServers": { "boundra": { "command": "uvx",
  "args": ["--from", "git+https://github.com/gobeyondfj-cmd/boundra", "boundra-mcp"] } } }

5 · Every payment gets a verdict before signing

Your agent calls evaluate_payment; the 5-stage pipeline answers ALLOW (sign & settle) / DENY (aborted pre-signature, zero on-chain trace) / ASK (a challenge bound to this exact payment).

6 · When the agent asks, you decide

uvx --from git+https://github.com/gobeyondfj-cmd/boundra boundra-approve

Paste the ASK challenge, sign it on your device — the agent retries with the signed approval token. Forged, rebound, or replayed tokens are rejected.

7 · Watch, update, revoke

get_spend_report / get_audit_trail / get_policy_versions keep you in control day to day. Every policy change is a new signed version (set_policy); revoke_policy is instant default-deny and free forever.

Quick start (from source)

cd boundra

# Mode 1: offline simulation (run this first — the full flow in 30 seconds)
python demo/demo.py

# Mode 2: real x402 + MCP
python -m venv .venv && .venv/bin/pip install \
    "x402[evm,httpx]" mcp eth-account fastapi uvicorn
.venv/bin/python tests/test_mcp_client.py    # MCP protocol-level tests
.venv/bin/python demo/setup_wallets.py       # generate Base Sepolia test wallets + faucet guide
.venv/bin/python demo/demo_real.py           # real protocol end-to-end (settles on-chain after funding)

Architecture: where the gateway stands

Agent framework (Claude / custom)
   │  MCP protocol (stdio)
   ▼
mcp_server.py  ──→  policy.py 5-stage evaluation pipeline
(policy decision     semantic → whitelist → limit → approval → budget
 point)
   ▲
   │ on_before_payment_creation hook (x402 SDK v2 native interception point)
x402_buyer.py ──sign (EIP-3009)──→ x402 server ──→ facilitator ──→ Base Sepolia

Key finding: x402 SDK v2 natively provides the on_before_payment_creation hook plus register_policy / set_spend_controls — the policy layer is not a bolt-on; it is the slot the official protocol stack reserves. This validates the wedge.

File map

boundra/
├── policy.py                 intent compilation (NL→Policy, bilingual CN/EN) + 5-stage pipeline + platform red lines
├── signed_policy.py          ★ signed policy documents + version chain + revocation (keccak)
├── approval.py               ★ signed approval tokens (challenge → user signs → gateway verifies)
├── mandate.py                ★ task Mandates: single-use authorization, burned after use (pipeline layer 4)
├── templates.py              ★ policy template library (personal assistant / travel / dev API / procurement)
├── chain_anchor.py           ★ anchor backends: local simulation + real Base Sepolia (web3)
├── gateway.py                gateway core v3: 4-layer stacking + token verification + Mandate + revocation
├── rail_adapters.py          ★ rail adapter layer: evaluation core decoupled from settlement rails (x402 first)
├── mcp_server.py             ★ standard MCP server (11 tools, stdio)
├── boundra_cli.py            ★ boundra-init (policy wizard) + boundra-approve (challenge signer)
├── contracts/
│   └── PolicyAnchor.sol      ★ on-chain commitment contract (owner-write, anyone-read)
├── demo/
│   ├── simulate_agent.py     ★ end-to-end user journey simulation (MCP + hosted API dogfood)
│   ├── demo_policy.py        signed-policy demo (impersonation / unsigned / tampering attacks all blocked)
│   ├── demo_real.py          real-protocol end-to-end orchestration
│   ├── x402_resource_server.py  real x402 paywall server (FastAPI middleware)
│   ├── x402_buyer.py         real x402 buyer, evaluated by the MCP gateway before signing
│   ├── setup_wallets.py      Base Sepolia test wallet generation
│   └── demo.py / merchant.py / agent.py   offline simulation (zero dependencies)
├── tests/
│   ├── test_product.py       ★ product tests (22 assertions)
│   └── test_mcp_client.py    MCP protocol-level tests
├── docs/
│   ├── dataflow.png          data-flow diagram (English)
│   └── render_*.py           diagram renderers (architecture / flow / use-case / data flow)
└── state/audit.jsonl         audit trail (generated at runtime, gitignored)

Signed policies: the root of trust is the user's key, not the gateway's database (v2)

A policy is a document signed by the user's wallet, not a row in the gateway's configuration:

user private key signature ──→ PolicyDocument (NL rule + compiled artifact + prev_hash + version)
                      │  three checks: signer == owner, versions sequential, prev_hash unbroken
                      ▼
              PolicyStore (version chain) ──→ LocalAnchor (simulated commitment; production writes to contract)
                      │
                      ▼  check_integrity before every evaluation (signature + anchor)
              5-stage pipeline; audit records cite policy version + hash

• Read-only for agents: without the user's private key, set_policy always fails — impersonation, unsigned, and tampered submissions are all blocked (seven scenarios in demo/demo_policy.py)

• Two stacked scopes: user-level (rules for all agents) × agent-level (per-agent rules); the strictest verdict wins

• Every version bump is a signature: v2 must reference v1's hash; tampering with any historical version → signature invalid + chain broken

• Privacy shape: only hash commitments go on-chain; policy plaintext never leaves the device unless the user chooses to disclose

Run: .venv/bin/python demo/demo_policy.py

MCP server tools

Mount into Claude Desktop

One line — uvx resolves dependencies and starts the server:

{
  "mcpServers": {
    "boundra": {
      "command": "uvx",
      "args": ["--from", "git+https://github.com/gobeyondfj-cmd/boundra", "boundra-mcp"]
    }
  }
}

On first run, use the boundra-init wizard (same package): create/import a wallet → pick a policy template → sign → publish via MCP, about 2 minutes. When your agent hits ASK, run boundra-approve and paste the challenge to produce a signed approval token.

⚠️ Known trust-boundary simplifications (must fix for production)

1. human_approved self-attested by the agent solved (v3): human approval is now a signed approval token (approval.py) — ASK returns a challenge bound to the exact payment intent; the user's device signs it; the gateway verifies signature + field-by-field intent match + nonce replay protection. The legacy self-attested path remains but is tagged approve(legacy-deprecated).

2. MCP-level interception is advisory — an agent framework can bypass the gateway and talk to the wallet directly. Mitigation: pair with x402's native hook (demonstrated in demo/demo_real.py; the hook fires inside the SDK, before signing). Endgame: compile the deterministic parts of policy into a smart-contract wallet module, enforced at the settlement layer.

3. Semantic detection is regex-based — production should swap in LLM evaluation + intent anchoring.

4. Anchoring defaults to a local log — the real contract (contracts/PolicyAnchor.sol) and web3 client (chain_anchor.BaseSepoliaAnchor) are ready; set chain_config.json to switch to the real chain (deploy via Remix with test ETH).

Economic model: the evaluation API is itself an x402 merchant

Tiered pricing:

Open core: the client, evaluation engine, and demos in this repo are Apache-2.0. The hosted evaluation service (tiered pricing, free-quota accounting, revenue ledger) runs from the private boundra-ops repo.

Verified / not yet verified

Verified (all of test_product.py 22 assertions + test_mcp_client.py pass): 4-layer policy stacking (platform red lines × user × agent × Mandate) with strictest-wins; signed approval tokens (valid passes, forged rejected, intent-rebinding rejected, replay rejected); Mandate single-use; revocation defaults to deny and a signed v2 restores; template render+compile; all MCP tools over the wire; gateway blocks an injection attack inside the real x402 402 round-trip before the SDK signs; the full tiered-pricing loop on Base Sepolia (2026-10-16): free tier passes, paid tier settles $0.003 USDC for real (buyer 20.000 → 19.997, platform address credited 0.003), dogfood hook self-evaluates, semantic layer blocks the injection, /revenue ledger entry. The settlement tx is publicly verifiable: 0x5ad8ef4b…c474bbe (the hosted service code is closed by design — the chain is the receipt).

Not yet verified: real on-chain anchoring (contract ready, needs test ETH to deploy); real user demand; semantic layer false-positive rate under real LLM behavior distributions.