Boundra — Payment Approval Gateway for AI Agents

Boundra · Payment approval gateway for AI agents

[Boundra on mcprush — Grade A, Trust 95/100]

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

[Boundra 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.

Integrating Boundra into your agent? See docs/INTEGRATION.md — hosted API, x402 SDK hook, and MCP paths with tested code.

See it run in 60 seconds

# 1. Hit the hosted evaluation API — a real, public x402 merchantcurl -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 — settled for real on Base mainnet (USDC)
# 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 wizarduvx --from git+https://github.com/gobeyondfj-cmd/boundra boundra-mcp     # stdio serveruvx --from git+https://github.com/gobeyondfj-cmd/boundra boundra-init    # wallet → template → sign → anchoruvx --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

Hosted (zero install, multi-tenant, default-deny until you publish a signed policy):

{ "mcpServers": { "boundra": { "url": "https://api.boundra.io/mcp" } } }

Or self-hosted:

{ "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 + MCPpython -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

Verdict credentials: every decision comes with a signed receipt (v4)

Every evaluate_payment response carries a credential — a boundra.verdict/v1 receipt signed by the platform key (EIP-191). It answers "who can prove this ALLOW / DENY / ASK actually happened, under this policy, for this exact payment intent?"

• Binds the intent: intent_hash = sha256 over the canonical {amount, recipient, purpose} — a credential cannot be re-attached to a different payment
• Binds the policy: policy_refs lists the policy version hashes used, comparable against on-chain anchors
• Binds the audit log: audit_id links to the server-side audit entry
• Verifiable offline, by anyone: strip proof, canonicalize the payload (sorted keys, compact separators), recover the EIP-191 signer — it must equal issuer and the platform address 0xF30955B6Be768370Da13fca237A5f252F6081d1C (the same address that receives x402 revenue — one identity for signing and settlement). Published at GET https://api.boundra.io/verdict-key.

from verdict_credential import verify_credentialok, why = verify_credential(verdict["credential"])   # offline, no API call

Self-hosted gateways attach no credential unless BOUNDRA_VERDICT_KEY is set — unsigned mode stays fully backward compatible.

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 — first proven on Base Sepolia (2026-10-16), then on Base mainnet (2026-10-21): free tier passes, paid tier settles $0.003 USDC for real (buyer 1.010 → 1.007, platform address credited 0.003), dogfood hook self-evaluates, semantic layer blocks the injection, /revenue ledger entry. The mainnet settlement tx is publicly verifiable: 0xf04d3497…4eac7e5 — the live API now settles on Base mainnet via Coinbase's CDP facilitator. Earlier testnet proof: 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.