pi-mpp-extension

MPP (Machine Payments Protocol) extension for Pi and OpenClaw. Lets the agent make paid HTTP requests to MPP-enabled services, handling the 402 Payment Required challenge flow automatically.

Install

git clone <this-repo> ~/.pi/agent/extensions/mpp
cd ~/.pi/agent/extensions/mpp
npm install

Or for project-local use:

git clone <this-repo> .pi/extensions/mpp
cd .pi/extensions/mpp
npm install

Quick test without installing globally:

pi -e ./index.ts

Payment Methods

Set env vars for whichever methods you want. Multiple can coexist — the SDK picks the right one based on what the server's 402 challenge offers.

Secrets

Credentials can be provided via env vars or a JSON secrets file (aligned with OpenClaw's source: "file" pattern):

export MPPX_SECRETS_FILE=~/.openclaw/mpp-secrets.json

The file uses env var names as keys:

{
  "MPPX_PRIVATE_KEY": "0x...",
  "MPPX_SPARK_MNEMONIC": "word1 word2 ...",
  "MPPX_ALLOWED_HOSTS": "api.example.com,mpp.dev"
}

Env vars take priority over the file. The secrets file should be chmod 600 — OpenClaw enforces this for its own secrets files.

Security

Host Allowlist

Strongly recommended for OpenClaw users. Without an allowlist, the agent can pay any MPP-enabled endpoint — including attacker-controlled services via prompt injection.

export MPPX_ALLOWED_HOSTS="api.example.com,mpp.dev,fal.mpp.tempo.xyz"

Supports subdomains — example.com allows api.example.com. If unset, all hosts are allowed.

Spend Guard

Pi TUI (interactive):

• First paid request prompts for confirmation
• At the limit, prompts to extend by another N requests
• Status bar shows MPP: tempo [3/10]

OpenClaw (headless):

• Auto-approves up to the limit (no UI to prompt)
• Hard-blocks at the limit
• Set MPPX_SPEND_LIMIT to control the ceiling

Tool

The extension registers a single tool: mpp_request

mpp_request({
  url: "https://api.example.com/resource",
  method: "POST",                          // optional, default GET
  body: '{"prompt": "hello"}',             // optional, JSON string
  headers: { "X-Custom": "value" }         // optional
})

The tool returns the response status, body, payment receipt (if paid), and running spend count.

How It Works

1. Agent calls mpp_request with a URL
2. Extension makes the HTTP request via mppx SDK
3. If the server returns 402 Payment Required, the SDK automatically:
   • Parses the payment challenge from WWW-Authenticate header
   • Fulfills payment using the configured method (Tempo, Stripe, Lightning, or Card)
   • Retries the request with a Authorization: Payment credential
4. Server verifies payment and returns the resource with a Payment-Receipt

Reference

• MPP Documentation
• mppx TypeScript SDK
• Pi Extension Docs

License

MIT