One-liner: Postman for HTTP 402 — the missing devtool for the Machine Payments Protocol.
Elevator pitch: HTTP 402 Payment Required has been "reserved for future use" since 1997. The Machine Payments Protocol finally uses it — enabling machines and AI agents to pay for API access programmatically. MPP Inspector is the developer toolkit that makes this protocol debuggable, testable, and visible from the terminal.
Category: Developer tools / Web3 DevEx / API debugging
Competitive position: There are no competing tools. The MPP ecosystem is early-stage, which means MPP Inspector can become the canonical developer tool — the equivalent of what Postman became for REST APIs or what Hardhat became for Solidity.
- People building MPP-compliant APIs on the Tempo chain
- Need to test that their 402 responses are correct
- Need to verify challenge headers, receipts, and pricing
- Size: Small (dozens to low hundreds today), but every one of them needs this tool
- Where they are: Tempo Discord, machinepayments.com community, GitHub
- Building autonomous agents that consume paid APIs
- The "machine payments" thesis: AI agents will need wallets and will pay for data
- Need to debug the payment handshake between agent and API
- Size: Growing rapidly (thousands of active builders)
- Where they are: r/LocalLLaMA, r/MachineLearning, AI agent Discords (AutoGPT, CrewAI, LangChain), Twitter/X AI dev community
- Building paid APIs on any EVM chain
- Interested in the 402 payment pattern as an alternative to API keys
- Size: Large (tens of thousands)
- Where they are: Ethereum, Base, Polygon developer communities, ETHGlobal
- Interested in HTTP protocol evolution
- The "HTTP 402 finally has a use" angle is inherently interesting
- Size: Niche but influential (blog posts from this group get amplified)
- Where they are: Hacker News, Lobste.rs, IETF mailing lists
Actions:
- Open an issue or PR on machinepayments.com repo to be listed as a community tool
- Message Tempo DevRel directly — offer the mock server as a testing resource for their docs
- Post in Tempo Discord
#dev-toolsor equivalent channel - Ask to be included in any "getting started with MPP" guides
Timeline: Week 1
Strategy: Short, visual, developer-focused posts. Show the terminal, not just text.
Post types:
- Launch post — terminal recording (Remotion video) showing
inspectparsing a live 402. Keep it under 45 seconds. - "Did you know?" series — "HTTP 402 has been reserved since 1997. Here's the protocol that finally uses it." + screenshot of inspect output.
- Comparison post — "Debugging a 402 challenge with curl vs mpp-inspector" side-by-side.
- Thread: "How machine payments work" — educational thread explaining the 402 flow, with mpp-inspector screenshots at each step.
Tagging strategy:
- Tag
@tempo_xyz,@machinepaymentson launch - Use hashtags:
#devtools,#web3,#machinelearning,#buildinpublic - Quote-tweet any MPP/Tempo announcements with the tool in action
Timeline: Launch post in Week 2, then 2-3 posts per week
Angle: "Show HN: MPP Inspector — A CLI to debug HTTP 402 Payment Required"
Post body draft:
HTTP 402 Payment Required has been in the HTTP spec since 1997, marked "reserved for future use." The Machine Payments Protocol (machinepayments.com) finally defines what that future looks like: machines paying for API access with on-chain tokens.
I built a CLI toolkit to debug and test this flow. It parses WWW-Authenticate: Payment challenge headers, verifies fields, discovers endpoints, and compares pricing across services.
Includes a mock server so you can try it without needing a live MPP endpoint:
npx @mpp-inspector/mock-serverthennpx mpp-inspector inspect http://localhost:3402/v1/queryGitHub: [link]
Timing: Post on a Tuesday or Wednesday, 9-10am US Eastern. Do NOT post until the mock server works and the README is polished.
Timeline: Week 3 (after mock server is published to npm)
Channels:
- r/LocalLLaMA — post when you have a working
flowcommand against testnet - AutoGPT Discord — mention in
#toolschannel - LangChain Discord — relevant if/when LangChain tools support paid APIs
- CrewAI community
Angle: "Your AI agent will need to pay for API access. Here's how to debug that payment handshake."
Timeline: Week 4+ (after flow command is complete)
Already done:
- Keywords updated:
mpp,machine-payments,http-402,payment-required,web3,tempo,blockchain,devtools,api-debugging,cli
Additional:
- Write a clear npm README (npm uses the root README by default — this already works)
- Publish
@mpp-inspector/mock-serveras a separate package
Blog post ideas:
-
"HTTP 402: The status code that waited 30 years"
- History of 402, what MPP does, how mpp-inspector makes it developer-friendly
- Cross-post to: dev.to, Hashnode, Medium
- Timing: Week 2-3
-
"Building a protocol debugger from scratch"
- Technical deep-dive: RFC 7235 parsing, challenge verification, CLI design
- Target: dev.to, personal blog
- Timing: Week 4
-
"Machine payments and the future of API monetization"
- Thought-leadership piece on why API keys might be replaced by on-chain payments
- Target: Medium, Hashnode, LinkedIn
- Timing: Week 6
- Add topic tags to the repo:
mpp,http-402,machine-payments,cli,devtools,tempo,web3 - Pin the repo on your GitHub profile
- Create 3-5 "good first issue" issues with clear descriptions:
- "Implement EIP-712 signature verification"
- "Parse /llms.txt into structured endpoints"
- "Add --format flag for custom output templates"
- "Add receipt persistence to local SQLite"
- "Support custom chain configuration via config file"
Duration: 45-60 seconds
Structure:
-
Hook (0-5s): "HTTP 402 has been reserved since 1997. It finally has a use." Text overlay on dark terminal background.
-
Problem (5-12s): Show a raw
curlresponse with a 402 and theWWW-Authenticate: Paymentheader. Highlight the wall of text. "This is what a machine payment challenge looks like. Good luck parsing that." -
Solution (12-35s): Type
mpp-inspector inspect http://localhost:3402/v1/query. Show the parsed, colored, verified output appearing. Hold for 3 seconds so viewers can read it. -
Discovery (35-45s): Type
mpp-inspector scan localhost:3402. Show the endpoint table appearing. "Discover every paid endpoint on any domain." -
CTA (45-55s): "npm install -g mpp-inspector" + GitHub URL. "Star if you think HTTP 402 deserves better tooling."
Visual style:
- Dark terminal background (One Dark or Dracula theme)
- Clean monospace font (JetBrains Mono or Fira Code)
- Minimal — let the terminal output speak
- Subtle typing animation (not too fast, not too slow)
- No background music — terminal sounds only (optional)
Variants:
- Full video for Twitter/X and YouTube
- 15-second cut for Reels/TikTok (just the inspect command)
- GIF of the inspect output for README and blog posts
- Publish mock server to npm
- Post in Tempo Discord
- Contact Tempo DevRel
- Add GitHub topic tags and pin repo
- Create "good first issue" labels
- Twitter/X launch post with terminal screenshot
- Create and publish Remotion demo video
- Publish blog post #1 ("HTTP 402: The status code that waited 30 years")
- Cross-post blog to dev.to and Hashnode
- Submit Show HN
- Twitter/X comparison post (curl vs mpp-inspector)
- Reply to any HN comments (critical for engagement)
- Share in relevant Reddit communities
- Publish blog post #2 (technical deep-dive)
- Post in AI agent communities (if
flowcommand is ready) - Twitter/X thread: "How machine payments work"
- Publish blog post #3 (thought-leadership)
- Monthly update post: new features, contributor shoutouts
- Revisit and refresh HN/Reddit if new features ship
- The core idea resonates
- Focus: is the README clear? Do people understand what this is?
- Start appearing in GitHub topic searches
- Focus: are people actually using it? Check npm download stats
- Action: create a
CHANGELOG.md, ship v0.2.0 with realflowcommand
- Worth a "trending" push
- Focus: contributor community. Are people opening issues and PRs?
- Action: add GitHub Discussions, write a "v1 roadmap" post
- Canonical tool for the MPP ecosystem
- Focus: ecosystem integrations (LangChain plugin, CI action, VS Code extension)
- Action: apply to be an official Tempo partner project
| Metric | Source | Check frequency |
|---|---|---|
| GitHub stars | GitHub repo | Weekly |
| npm weekly downloads | npmjs.com/package/mpp-inspector | Weekly |
| GitHub traffic (views, clones) | Repo → Insights → Traffic | Weekly |
| Referral sources | GitHub traffic insights | Bi-weekly |
| Issues opened | GitHub notifications | Daily |
| HN/Reddit post performance | Post analytics | Day-of and day-after |
| Twitter impressions | Twitter Analytics | After each post |
| Blog post views | dev.to / Hashnode dashboards | Weekly |
- Show, don't tell. Terminal recordings beat feature lists. A working demo beats a description.
- Time the narrative. Don't promote
flowuntil it actually executes payments. Don't promotesessionuntil channels work. Credibility is fragile. - Ride the wave. Every Tempo announcement, every AI-agent-pays-for-API story is a distribution opportunity. Quote-tweet with the tool in action.
- Contribute upstream. Help improve the MPP spec docs. Being a contributor to the protocol itself makes the tool more credible.
- Be the canonical source. Write the best explanation of "how HTTP 402 works with MPP" on the internet. If someone Googles it, your blog post should be the top result.