PayStage Preflight

io.github.base-buzzPublished by GitHub account base-buzzv0.2.3Updated Nov 12, 2026

Evaluate x402 PaymentRequired against a local spending policy before an agent pays

The publisher's own server: Preflight

VerifiedSTDIODesktop onlyFinance Security & Monitoring

Server details

Identifier: io.github.base-buzz/preflight
Transport: STDIO
Runtime: Desktop only
Trust: Verified
Published: Nov 12, 2026

Security note

MCP servers receive tool arguments from a conversation and may perform external actions. Review what a server can do before you enable it, and give it only the access it needs.

The registry verified the GitHub account base-buzz for this listing. That does not show the account is the product's maker.

SourceWeft's checks cover whether the listing is complete and the endpoint answered; they do not review the server's code or what its tools do.

Add a badge to your README

Show readers this MCP server is listed on SourceWeft. The badge links to this page.

[![Listed on SourceWeft](https://sourceweft.com/badge/mcp/io.github.base-buzz%2Fpreflight.svg)](https://sourceweft.com/mcp/io.github.base-buzz%2Fpreflight?utm_source=readme&utm_medium=badge)

Overview

AI-generated overview

A local stdio MCP server that checks an x402 PaymentRequired payload against a JSON spending policy and returns pay, review, or do_not_pay before an agent pays.

What you can do: Evaluate a payment request: check an x402 PaymentRequired payload against the local policy and get one of three verdicts — pay, review, or do_not_pay.
Apply spending rules: allowed networks, assets and payees, per-call and per-session amount caps, a human-review threshold, and a maximum timeout.
Flag malformed or out-of-policy requests as do_not_pay, and requests above the human threshold as review.
When to use it: Use it when an agent can make x402 payments and you want a deterministic, local check that blocks or escalates payments outside your rules before any money moves.
Requirements: Node.js with npx to run the npm package locally over stdio, plus a policy JSON file whose absolute path is set in PAYSTAGE_POLICY_PATH. No account, API key or network access is needed to decide.

Before you install

The verdict is advisory: it does not itself pay or hold funds, so the client must actually honor pay, review and do_not_pay. Policy mistakes (wrong networks, assets, payees or caps) directly change what gets approved, so review the policy file carefully. The README notes the package reads the policy file and PAYSTAGE_POLICY_PATH, and mentions PAYSTAGE_RPC_URL used by a related package.

Installation

In SourceWeft

Open PayStage Preflight in the dashboard and add it to a workspace.
Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

@paystage/preflight

Evaluate an x402 PaymentRequired against a local spending policy before your agent pays. Returns one of three verdicts: pay, review, or do_not_pay.

Local-first — policy lives in a JSON file on your machine. No secrets, no network calls to decide.
MCP-native — runs as a stdio MCP server so Claude Desktop, Cursor, and any MCP client can call it as a tool.
Deterministic — same input + same policy ⇒ same verdict.

Install

Run directly with npx (no global install):

Or add it to your MCP client config.

Claude Desktop

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"      }    }  }}

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

Cursor

Add to .cursor/mcp.json:

json

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

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

Example `policy.json`

json

{  "version": 1,  "name": "standard",  "allowed_networks": ["eip155:8453", "eip155:84532"],  "allowed_assets": [    "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",    "0x036CbD53842c5426634e7929541eC2318f3dCF7e"  ],  "allowed_pay_to": ["0x209693Bc6afc0C5328bA36FaF03C514EF312287C"],  "max_amount_per_call": "1.00",  "max_amount_per_session": "10.00",  "require_human_above": "0.50",  "max_timeout_seconds": 300,  "default_verdict": "review"}

{  "version": 1,  "name": "standard",  "allowed_networks": ["eip155:8453", "eip155:84532"],  "allowed_assets": [    "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",    "0x036CbD53842c5426634e7929541eC2318f3dCF7e"  ],  "allowed_pay_to": ["0x209693Bc6afc0C5328bA36FaF03C514EF312287C"],  "max_amount_per_call": "1.00",  "max_amount_per_session": "10.00",  "require_human_above": "0.50",  "max_timeout_seconds": 300,  "default_verdict": "review"}

Amounts are human-readable USDC (e.g. "0.50" = 0.50 USDC). Networks use CAIP-2 identifiers.

Verdicts

Verdict	Meaning
`pay`	Within policy — safe to proceed automatically.
`review`	Allowed but above a human threshold — ask a human before paying.
`do_not_pay`	Violates policy (network, asset, payTo, amount, timeout, or malformed).

Supply chain and access

Socket.dev scores this package on what it can do, not what it does with it, so the flags it raises are worth explaining rather than removing:

Flag	Why it is there
Filesystem access	Reads the policy JSON you point it at (`policy_path` / `PAYSTAGE_POLICY_PATH`). Nothing is written.
Environment variable access	`PAYSTAGE_POLICY_PATH` only (and `PAYSTAGE_RPC_URL` via `auth-watch`).
Network access, URL strings	None in this package. The RPC endpoints you may see in the tree belong to `@paystage/auth-watch`.

No shell, no eval, no telemetry, no key custody. The full table is in SECURITY.md; the deny list is published with a citation per entry in KNOWN_DRAINERS.md.

Tools

evaluate_mcp_payment

Evaluate an x402 PaymentRequired payload against a PayStage spending policy before paying

Parameterspolicypolicy_pathpayment_requiredrequired

Version history

v0.2.3LatestNov 12, 2026

Score

90% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

Reached in the last 30 days25 pts
Auth declared10 pts
Declare the credential headers in the registry entry, or keep the endpoint answering the probe so its auth can be classified.
Tools listedRequired15 pts
DescriptionRequired15 pts
Logo10 pts
Documentation15 pts
License10 pts

Other Preflight integrations

Preflight

social.preflightOfficial publisher

Hosted social media scheduling server that lets an assistant draft, rule-check, schedule and publish posts to 12 networks.

Streamable HTTPWeb executableAuth

Productivity & WorkflowCredential requiredOct 27, 2026

Preflight

Published by GitHub account dainidude

Remote MCP server that gives an assistant pay-per-call smart-contract security checks: Solidity scans, transaction simulation and token risk verdicts.

Streamable HTTPWeb executable

Finance4 toolsNov 14, 2026