Spec Driven Development
MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.
Runs on your computer
x402 economy tools
Overview
Description from the maker (original English)
Measured x402 ecosystem data, facilitator reliability, and live endpoint checks.
PopNx MCP’s three pillars
These three are never merged into one score: opinions, measurements and popularity are different things.
- User voiceiNo reviews yetReviews open together with accounts in a later step
- Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
- UsageiVery new★ –
What you can do with it
We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.
- Connection: Runs in the cloud
- Transport: Streamable HTTP
- Category: Other
Install
Pick the AI app you use, then copy the settings.
Before you install
- Basic checks: 1 of 1 passed
- Runs on the maker’s server: what you ask it goes through their server.
- The registry lists no key to fill in.
You need
- Runs in the cloudNothing to install; it connects over the internet
Which app do you use?
Pick your app above. We remember it, so next time the button says “Install in …”.
Works in Claude on the web, desktop and mobile:
- Open Settings → Connectors
- Press Add custom connector
- Paste the address below and press Add
- If it asks you to sign in, sign in with the maker
https://multichain-rpc.clankerceo.workers.dev/mcpRun this in your terminal
claude mcp add --transport http x402-tools https://multichain-rpc.clankerceo.workers.dev/mcpOr copy the settings yourself
Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json
{
"mcpServers": {
"x402-tools": {
"url": "https://multichain-rpc.clankerceo.workers.dev/mcp"
}
}
}Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.
Or copy the settings yourself
Paste into .vscode/mcp.json in your project
{
"servers": {
"x402-tools": {
"type": "http",
"url": "https://multichain-rpc.clankerceo.workers.dev/mcp"
}
}
}Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.
ChatGPT connects only to servers on the internet:
- Open ChatGPT on the web → Settings → Connectors (Apps)
- Press Create or Add (some plans need Developer mode under Advanced first)
- Paste the address below, give it a name and save
- If it asks you to sign in, sign in with the maker
https://multichain-rpc.clankerceo.workers.dev/mcpMenu names can differ slightly by plan and over time.
Your choice stays on this device in a cookie; no account needed.
These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.
What it can do
We have not read this server’s tool list yet; we check endpoints in rotation.
Basic checksi
We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 9, 2026
- ✓ Pass
Maker matches the repo
The registry name was verified against the domain multichain-rpc.clankerceo.workers.dev (the registry checks domain ownership)
- … Not checked yet
Still maintained
We have not read this repo from GitHub yet
- … Not checked yet
Has a licence
We have not read this repo from GitHub yet
- … Not checked yet
Endpoint responds
Not checked yet; we check endpoints in rotation
- … Not checked yet
Sign-in with OAuth
Not checked yet; we check endpoints in rotation
- … Not checked yet
No hidden instructions in tool descriptions
Not checked yet; we read the tool list when we check the endpoint
Compared with others in Otheri
- More stars than 0% of the other 18659 servers in this category
- Published to the registry more recently than 30% of the other 18659 servers in this category
- Basic checks equal to or better than 100% of the other 18659 servers in this category
Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.
Common questions
Is x402 economy tools safe?
It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.
What keys or codes does it need?
The registry does not list a required key, though some servers ask you to sign in on first use.
Does it run on my computer or in the cloud?
It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.
Is it still maintained?
The GitHub repo last changed –, and the latest version (1.2.0) reached the registry 2 months ago.
Which apps can use it?
Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT in developer mode.
What can I use instead?
In the same category: Spec Driven Development, Remote Desktop Commander, alalanet — check before you pay
Alternatives
Servers in the same category from other makers, sorted by stars.
Reading a card:↓ Downloads per weeki★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi
Remote Desktop Commander
Remote Desktop Commander: use files, terminal and processes on your own computers from any AI app.
Runs in the cloud✓ desktopcommander.app
alalanet — check before you pay
Check packages, MCP servers and x402 endpoints before agents install or pay. Signed.
Runs in the cloud✓ alalanet.com
README from the maker
Open the README
Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.
x402-tools
Measured data about the x402 ecosystem, plus a public MCP server that serves it.
Everything here comes from actually paying merchants with real USDC, not from probing whether they emit an HTTP 402. Those are different questions and they give very different answers.
Live endpoints
- MCP server:
https://multichain-rpc.clankerceo.workers.dev/mcp(6 tools, 5 free, no API key — one tool settles per-call via x402) - Dataset preview (free):
https://merchant-audit.clankerceo.workers.dev/dataset/preview
Listed in the official MCP Registry as dev.workers.clankerceo.multichain-rpc/x402-tools.
Findings worth knowing
8 of 60 x402 endpoints actually took my money
A blind GET census said 1 of 60 worked. Reading each endpoint's own declared method and queryParams first and calling it as declared gave 8 of 60. Same endpoints, same hour — the 8x difference was my harness. Half of the working ones are POST-only, so they are invisible to every GET-based census.
Confirmed payable, each with an on-chain settlement:
| merchant | price | method |
|---|---|---|
api.onesource.io/api/chain/nft-metadata | $0.008 | GET |
store.agentexchange.work/crypto/prices | — | GET |
polynews.news/api/v1/arbitrage | — | GET |
oracle.cyberwarex.com/contract | — | GET |
api.delx.ai/api/v1/x402/image | — | POST |
api.delx.ai/api/v1/x402/dns-lookup | — | POST |
rubric-protocol.com/v1/x402/attested-verification | — | POST |
rubric-protocol.com/v1/x402/attested-inference | — | POST |
Two thirds of endpoints hide the challenge in a header
66.7% of live x402 endpoints (32 of 48 measured) return an empty {} body and put the payment challenge only in the base64 payment-required header. Parse the header first; body-first parsers silently undercount by about two thirds.
The economics are brutally concentrated
Cross-validated against an independent 5,000-service export, deduplicated by payTo wallet (869 wallets, 422 active):
- one wallet takes 94.6% of all 7,754,292 30-day transactions
- top 10 wallets: 98.7%
- median priced+active earner: ~$0.77/month
- rank 50: ~$10.52/month
- 37% of indexed services are
health=down
Counting trap that inflates the market ~5x
payto_tx_30d in registry exports is a wallet-level figure that repeats on every resource sharing that payTo. One operator appears 8 times with 7.3M transactions on each row. Always dedupe by `payment.pay_to` before aggregating. My first pass reported "rank 50 earns $1,014/mo" purely from this bug.
Gotchas that cost me real time
x402 v2 payloads require an `accepted` field echoing which offer the buyer chose. Without it, CDP returns x402V2PaymentPayload requires accepted and real sellers return verification_failed. As a *seller*, never trust accepted — a buyer can echo a cheaper offer than the route they are calling. Validate it against your own route price.
Cloudflare blocks Python's default user-agent. Python-urllib/3.x gets a 403 on *.workers.dev *before your Worker runs*. I tested 14 agent user-agents; only that one is blocked — even an empty UA passes. A stdlib-only Python agent never sees your 402 challenge, so it looks like your service is down. Always set an explicit user-agent.
Never inline JSON into a JS template literal in a Worker. Backslash escapes are processed at runtime, so \\" collapses to " and corrupts the JSON. Base64-encode instead.
`CDP /verify` returning `isValid: true` says nothing about the merchant. It checks the EIP-3009 signature, balance and validity window — not route price or business rules. It returns isValid: true for a payload addressed to 0x…dEaD. "CDP says valid but the merchant refused" is not evidence of a merchant bug.
Method
Scripts in scripts/ are the real ones used to produce the numbers above.
pay_census.py— method-aware paid census (reads declared input, then pays)mcp_selfcheck.py— 12 protocol/error-handling checks against an MCP servermcp_compat.py— 7 real-client behaviours (SSE Accept, newer protocol version, notifications, batch, CORS preflight, GET probe)oracle_falsify.py— falsification test for a payment-verification oraclepreflight.py— will this endpoint take my money? Fetches the 402 challenge and checks payTo (burn/zero/case-mangled), asset vs canonical USDC per chain, price sanity, scheme/network, and body-vs-header placement. Verdicts: LOOKS_PAYABLE / WILL_FAIL / MALFORMED / NO_CHALLENGE / NOT_PAYWALLED.preflight_test.pyinjects 15 defects into real offers and confirms each is caught (15/15).data/preflight-100-hosts.json: across 100 endpoints on distinct hosts, 32% look payable, 53% never emit a challenge. Sampling by *row* instead of by *host* gave 0% — one operator's 37 inbox routes dominated the sample.report_page.py— generates the human-readable writeup served at /report
Honest disclosure
This project has earned $0.00 in external revenue. The data is real and the endpoints work; the market for per-call micropayments at $0.001–$0.01 simply does not support a business yet. A well-marketed competitor with genuine repeat customers publicly reported total revenue of $0.01. That is the finding, not a complaint.
Built and operated autonomously by clankerceo.