IntentFence Payment Firewall README
The full upstream README, mirrored here for reference. Install config, tool schemas, adoption signals, and an original overview live on the IntentFence Payment Firewall listing page.
IntentFence
IntentFence is a fail-closed authorization firewall for autonomous AI agents. Immediately before a consequential MCP, HTTP, A2A, or payment action, it binds the exact action and payload hash to explicit action/resource allowlists, spend and retention ceilings, and optional action-specific approval. It returns a five-minute ES256 receipt; the TypeScript and Python SDKs verify the receipt and local action digest before executing the caller-owned callback. IntentFence never executes downstream tools and should never receive credentials or wallet keys. It also provides MCP metadata scanning and x402 payment-safety checks.
safe_to_proceedneeds_reviewdenied
Production: https://agentpass-protocol.rmalka06.chatgpt.site
x402scan: https://www.x402scan.com/server/c495c104-dba4-4764-86b1-96b8b0cda48b
Official MCP Registry: https://registry.modelcontextprotocol.io/v0.1/servers?search=io.github.razel369%2Fintentfence
Protocol surfaces
| Surface | Endpoint |
|---|---|
| Action-bound authorization | POST /api/actions/authorize |
| Paid self-service production policy pack | POST /api/policy-packs |
| Free MCP metadata risk scan | POST /api/agent-risk/scan |
| Free REST preview | POST /api/preflight |
| Paid x402 decision | POST /api/preflight/verified |
| Paid caller-observed x402 quote assessment | POST /api/x402-assessments |
| Paid live x402 endpoint readiness | POST /api/x402-readiness |
| Paid live Base wallet-risk assessment | GET /api/wallet-risk?address=... |
| Paid signed official U.S. CPI data | GET /api/us-cpi?month=YYYY-MM |
| Receipt verification | POST /api/receipts/verify |
| Public ES256 keys | GET /.well-known/jwks.json |
| MCP Streamable HTTP | /api/mcp (intentfence_verified_preflight is x402-paid) |
| A2A Agent Card | GET /.well-known/agent-card.json |
| x402 service manifest | GET /.well-known/x402 |
| Public aggregate metrics | GET /api/metrics |
| OpenAPI | GET /openapi.json |
Fail-closed action authorization
The hosted MCP tools intentfence_authorize_action and
intentfence_agent_risk_scan are available without an API key and are
rate-limited. Authorization signs the exact caller-supplied action and policy
digests for five minutes but does not validate the truth of a self-declared
identity or approval source. Production callers must verify the receipt,
re-hash the local action, and block on denial, review, expiry, mismatch, network
failure, or verification failure. Use the TypeScript enforceAction or Python
run_authorized helper to make that boundary executable.
The scanner evaluates caller-supplied MCP metadata only. It highlights missing schemas, annotations, action-bound approval, and financial limits, but does not execute tools, inspect source code, or certify security or compliance.
Official U.S. CPI costs 0.001 USDC; live readiness and wallet risk cost 0.002 USDC; signed preflight and exact-quote assessment cost
0.005 USDC on Base through x402. A successful call
returns both the facilitator's PAYMENT-RESPONSE settlement header and an
IntentFence ES256 compact-JWS receipt.
Wallet risk is the recommended first check before paying a Base recipient. It
uses live Base RPC activity and GoPlus malicious-address intelligence. A
safe_to_proceed result means no listed malicious flags were observed and the
address was established on Base at assessment time; it does not prove identity,
ownership, authorization, or future behavior.
Install the recurring pre-payment skill to attach that check to new Base recipients:
The skill can run without interrupting an autonomous workflow only when the wallet owner already approved a standing 0.002 USDC screening budget and the wallet enforces it. It blocks the downstream payment on review, denial, missing settlement proof, invalid receipt, or service failure.
The live readiness check is the simplest first call when an agent only has an endpoint URL. It makes one bounded credential-free request, rejects private-network targets and redirects, validates the returned challenge, never pays the target, and signs the result for five minutes.
The quote assessment is the recommended check after an x402 merchant returns
its unpaid challenge and before the agent signs the merchant payment.
The agent supplies subject, target_url, optional method (GET, HEAD, or
POST), the base64 payment_required header (maximum 16 KiB), and a policy with
max_price_usdc plus an optional allowed_payees list. IntentFence validates
x402 v2, exact scheme, Base mainnet, canonical Base USDC, price, payee, and exact
resource binding. It requires the canonical USDC EIP-712 domain and sends
Permit2, unknown transfer metadata, and active extensions to review. A
safe_to_proceed result requires an explicit matching
allowed_payees entry; omitting the list yields needs_review. IntentFence
never fetches or pays the target. Every advertised payment option must satisfy
every automatic check; mixed safe and unsafe option sets are denied.
Self-service production policy pack
An agent or developer can buy a complete production guard without an account, email, meeting, or sales call:
The request selects openai-agents-js, cloudflare-agents,
coinbase-agentkit, or mcp-gateway and supplies one exact action plus its
allowlists, spend ceiling, retention limit, and optional approval policy. The
first request returns an x402 challenge for exactly 1 USDC on Base. After
settlement, the same response delivers a copy-ready TypeScript guard, signed
action and policy receipt, allowed/denied/over-budget test vectors, and a
fail-closed deployment checklist. The buyer must review the generated code and
keep all credentials in its own runtime.
Install now
The hosted MCP endpoint is available without an API key:
Install the local stdio MCP package
Agents and MCP clients that require a local process can run the immutable public 0.11.0 release directly. This does not require an npm account, repository clone, or IntentFence API key:
The release artifact is built and tested by GitHub Actions. Its SHA-256 digest
is f0cdf3df28da8a5c037e48193cbb4602744b5fb0b6c182d877abedb707b1e9f9.
Use the hosted endpoint above when the client supports Streamable HTTP.
Install in an agent runtime
- OpenAI Agents SDK fail-closed guard
- Cloudflare Agents fail-closed guard
- Coinbase AgentKit pinned x402 checkout
- Generic MCP gateway guard
All adapters keep credentials in the caller runtime and execute the downstream action only after the exact local action digest and ES256 receipt verify.
Opt-in one-call payment for local agents
The local stdio package can handle the x402 challenge, sign it, retry the tool call, and return the settled result without requiring special MCP-client support. Automatic payment is disabled unless all three values below are set:
Supply the key through the agent runtime's secret manager or process
environment; never commit it to an MCP configuration file. The package signs
only exact Base-mainnet USDC requirements addressed to the published
IntentFence recipient, rejects any payment above the per-call ceiling, and
reserves every attempted signature against the process-lifetime budget before
signing. Failed attempts remain reserved, so retry loops and concurrent calls
cannot exceed the cap. The private key stays in the buyer's local process and is
never sent to IntentFence.
Build an exact machine checkout
Agents do not need to infer which endpoint, method, payload, or payment cap matches a product. Read the catalog, then submit the exact product input:
The checkout response is free and never initiates payment. It returns a
validated HTTP request, shell-safe Agentic Wallet argv, POSIX and PowerShell
commands, Coinbase Agentic Wallet MCP instructions, an mcpc --x402 call, the
matching Agent Skill, the matching MCP tool and arguments, and an exact Base
USDC ceiling. Paid MCP tools advertise _meta.x402 for clients that can sign
before the first tool call.
Agents must still review and authorize the payment and require
PAYMENT-RESPONSE settlement proof.
Install in VS Code
Open the live install panel, then select Install IntentFence in VS Code.
The install action contains only the public server name, transport, and URL. VS Code asks you to review and trust the server before its first start. The free policy-preview tool works with no API key. Paid calls through the hosted server need an x402-capable client; runtimes without one can use the budget-capped local stdio mode above.
Manual .vscode/mcp.json or user-profile fallback:
Review the server details yourself before starting a manually configured server.
See the official VS Code MCP installation documentation.
Install the cross-agent payment guard
Install the open Agent Skill in Codex, Claude Code, Cursor, Gemini CLI, GitHub Copilot, and other skills-compatible agents:
Review the complete skill before installing it.
The skill triggers when an agent is about to sign an x402 payment. It teaches the agent to capture the exact quote, enforce a caller-defined ceiling and payee allowlist, keep wallet credentials local, and use IntentFence only after the 0.005 USDC assessment fee is authorized. It includes a capped Coinbase Agentic Wallet buyer path for agents that already use an authenticated wallet.
Agents that have only a public x402 URL can install the narrower live-readiness skill. It probes the route without credentials or target payment, blocks redirects and private-network targets, validates the returned challenge, and requires explicit authorization before the 0.002 USDC IntentFence fee:
The official x402 client buyer example verifies the live fee challenge before creating a signer and is payment-disabled by default:
https://github.com/razel369/intentfence/tree/main/examples/x402-buyer
Agents that already use Coinbase Agentic Wallet can retrieve a complete capped
checkout from GET /api/payments under buyer_quickstart. The published
command is pinned to a verified CLI version, includes a valid policy body, and
sets --max-amount 5000 so it cannot authorize more than the 0.005 USDC
IntentFence fee. Review the body and explicitly authorize the real payment
before running it.
Projects that already own a Coinbase AgentKit EVM wallet can use the pinned AgentKit adapter. Unlike an automatic retry, it binds the payment to the exact IntentFence URL, Base network, canonical USDC asset, 5000-atomic-unit amount, and recipient, then calls the buyer's own authorization function before signing. The matching machine-readable manifest is published at https://agentpass-protocol.rmalka06.chatgpt.site/integrations/coinbase-agentkit.json.
Gemini CLI can install the repository directly, without waiting for an npm package or gallery crawl:
The extension starts a dependency-free local MCP bridge and exposes the free preview plus the x402-paid verified preflight and quote-assessment tools.
Caller-observed x402 quote assessment
The first call returns the standard PAYMENT-REQUIRED challenge for the
IntentFence fee:
Retry the same request with a valid x402 v2 PAYMENT-SIGNATURE. A successful
response contains the validated caller-observed challenge fields,
pass/review/deny checks, a SHA-256 binding to the full target URL and exact
payment requirement, and an ES256-signed assessment receipt. The assessment
uses assurance caller-observed-x402-quote-assessment and verification tier
x402-quote-assessment+x402-settled; x402 settlement covers the 0.005 USDC
IntentFence assessment fee, not the target payment.
Live Base wallet risk
The first call returns an x402 challenge for 0.002 USDC:
Retry the same URL with a valid x402 v2 PAYMENT-SIGNATURE. The successful
response includes Base account activity, native and USDC balances, a code hash
for contracts, current malicious-address flags, pass/review/deny checks, and a
five-minute ES256 receipt with assurance live-base-wallet-risk. If a required
live source is unavailable, the endpoint fails closed and does not intentionally
settle the assessment fee.
Important trust boundary
Declared-input receipts attest only that IntentFence evaluated caller-supplied
policy data. Quote-assessment receipts bind the exact caller-observed
PAYMENT-REQUIRED challenge; they do not prove that IntentFence contacted the
merchant, or prove merchant identity, delivery, or downstream enforcement. The
receipt-signing key is separate from the USDC recipient wallet. IntentFence
never needs a payer's seed phrase or wallet private key. Wallet-risk receipts
report observed evidence at one point in time and are not identity attestations.
Local development
For MCP clients that launch local stdio servers, use npm run mcp:stdio.
Glama and other container-based hosts can build the root Dockerfile; it starts
the same IntentFence policy engine and responds to MCP initialization,
tools/list, and tools/call requests over standard input/output.
The production signing key is stored in Sites as the secret
INTENTFENCE_SIGNING_PRIVATE_JWK. Generate a separate development key with:
Never commit the generated private JWK. Publish only its public coordinates in
/.well-known/jwks.json.
Validation
Set INTENTFENCE_TEST_PRIVATE_JWK_PATH only for a local smoke test that should
exercise the signed-receipt verifier.
Distribution
TypeScript and Python SDKs live in sdk/. The root server.json is ready for
the official MCP Registry under io.github.razel369/intentfence; the public MCP
endpoint uses Streamable HTTP and requires no API key.
The /.well-known/x402 service manifest and Bazaar metadata make both paid
endpoints crawlable by x402 indexes and autonomous tool routers. Production
resources are continuously checked, and the original verified-preflight route
is registered on x402scan.
Production uses PayAI by default. When both CDP_API_KEY_ID and
CDP_API_KEY_SECRET are configured in the hosted runtime, verification and
settlement switch to Coinbase CDP. That makes successful Bazaar-enabled route
settlements eligible for Coinbase Bazaar indexing; configuration alone does
not create a listing or count as customer revenue.
Commercial path
The fastest no-contact path to production is the 1 USDC policy pack for one
guarded purchase, transfer, booking, deployment, deletion, or other
consequential action. The machine-readable offer and capped Agentic Wallet
checkout are published by GET /api/payments.
See docs/PROTOCOL.md and docs/SECURITY.md for the protocol and security model.