# PayStage

> Safety tools for AI agent payments (x402 + MCP). Preflight checks that decide whether an agent should pay, pause for review, or refuse.

Status: early. The MCP payment preflight server is **Available soon** and is **not yet published to npm**. Do not assume `npx` install works today.

## What PayStage does

AI agents increasingly move money — paying for API calls over x402, settling in USDC on Base, and calling tools over MCP. PayStage sits in front of those payments and answers one question: should this payment happen?

The preflight server evaluates a proposed payment against a local policy file and returns a verdict:

- `pay` — within policy, safe to proceed
- `review` — needs human or higher-level approval
- `do_not_pay` — blocked by policy

## Tools

- MCP payment preflight (`@paystage/preflight`) — Available soon (not yet published to npm)
- Policy engine for x402 payments — Roadmap
- Payee allowlist / reputation checks — Roadmap
- Spend limits and budget guardrails — Roadmap
- Audit log for agent payments — Roadmap

## Install (coming soon)

Not yet published to npm. Once released:

```
npx -y @paystage/preflight
```

## Claude Desktop config

Add to `claude_desktop_config.json`:

```json
{
  "mcpServers": {
    "paystage-preflight": {
      "command": "npx",
      "args": ["-y", "@paystage/preflight"],
      "env": {
        "PAYSTAGE_POLICY_PATH": "/absolute/path/to/policy.json"
      }
    }
  }
}
```

## Cursor config

Add to `.cursor/mcp.json` (or Cursor settings → MCP):

```json
{
  "mcpServers": {
    "paystage-preflight": {
      "command": "npx",
      "args": ["-y", "@paystage/preflight"],
      "env": {
        "PAYSTAGE_POLICY_PATH": "/absolute/path/to/policy.json"
      }
    }
  }
}
```

## Example policy.json

```json
{
  "max_amount": { "value": "5.00", "asset": "USDC", "decimals": 6 },
  "allowed_pay_to": ["0x0000000000000000000000000000000000000000"],
  "allowed_networks": ["eip155:8453", "eip155:84532"],
  "unknown_payee": "review"
}
```

Fields:

- `max_amount` — object with `value` (decimal string), `asset` (e.g. `USDC`), `decimals` (integer)
- `allowed_pay_to` — list of payee addresses permitted without review
- `allowed_networks` — CAIP-2 network IDs; `eip155:8453` is Base mainnet, `eip155:84532` is Base Sepolia
- `unknown_payee` — verdict to return for payees not in `allowed_pay_to` (`review` recommended)

## Verdict table

| Verdict | Meaning | Typical cause |
| --- | --- | --- |
| `pay` | Proceed | Amount within limit, payee allowed, network allowed |
| `review` | Pause for approval | Unknown payee, near-limit amount, unusual network |
| `do_not_pay` | Block | Over limit, disallowed network, explicit deny |

## Environment

- `PAYSTAGE_POLICY_PATH` — absolute path to `policy.json`. Required.

## Links

- Website: https://paystage.xyz/
- Repo: https://github.com/base-buzz/paystage
- Preflight README: https://github.com/base-buzz/paystage/blob/main/packages/preflight/README.md
- Preflight server.json: https://github.com/base-buzz/paystage/blob/main/packages/preflight/server.json
- Compact doc: https://paystage.xyz/llms.txt