GET /headless Digest #1 — GET /headless

/headless tidbits

Anthropic acquires Stainless for $300M+. (source). Stainless turns an OpenAPI spec into SDKs across several languages, plus adding CLIs and MCP servers, all auto-generated and kept in sync as the core API evolves. This article has a good explanation of what this means.

Every official Anthropic SDK was built with it, as were OpenAI’s, Cloudflare’s, Runway’s and 100s of other AI startups. Anthropic will wind down the hosted product and competitors lose access. This is Anthropic’s fourth acquisition in six months (after Bun, Vercept, and Coefficient Bio).

The HN thread is worth reading, with the first comment likely nailing the rationale and lessons:

Anthropic is at a place where they need the world’s best software engineers, and they’re willing to comp at insane levels to get them. However: You simply cannot post a Linkedin job for “Really Good Software Engineer, comp $10M+” and make any sense of the inbound applications you’ll get. They’re not the first to figure this out, and they won’t be the last: Successfully building a company, and using that company’s products, is actually the best job interview you can ask for if you can pay for that caliber of candidate.

What you should be paying attention to: Stainless is shutting down, and their team is joining Anthropic to build, who knows, some dumb integration to make Hubspot data available in Claude, or something equally as boring. But, Stainless was successful. Be the next Stainless. The idea is already validated, these AI companies have already done this to a handful of companies and they’re going to keep doing it.

My Take

The hosted product alone probably wasn’t worth $300M but Anthropic is buying a team of excellent software engineers (and former Stripes!) that knows how to make every API agent-accessible. That capability is being pulled from OpenAI, and other competitors in the process. It’s also another indicator how important the headless economy is becoming. API, SDKs, CLIs, MCPs are the first layers of agent accessibility. Anthropic themselves put it in their announcement: “The frontier of AI is shifting from models that answer to agents that act.” If agents run on APIs, owning the SDK-and-MCP generation layer is a real chokepoint.

I wonder (1) who is going to replace Stainless now and (2) what other “Stainlesses” are still being developed, for various domains. Reach out to me if you find more.

Parallel launches Index for content attribution in the agent economy. Index is a new platform from Parallel Web Systems (former Twitter CEO Parag Agrawal’s startup, $100M raised) that helps content owners track and get compensated for how AI agents use their work. Compensation is calculated using Shapley values, estimating each source’s marginal contribution to what an agent produces at inference time. Launch partners include The Atlantic, Fortune, PitchBook, ZoomInfo, and newsletters like Every, Exponential View, and Not Boring.

MCP Watch. Salesforce shipped Data 360 MCP as an open-source developer preview (following Headless 360 at TDX). Ashby added MCP support to its ATS. Pacvue launched an MCP server for commerce media data across Amazon, Walmart, Instacart, Kroger, and Target.

Stripe ungates the Machine Payments Protocol. MPP is an open standard co-authored by Stripe and Tempo that gives agents a native way to pay for services programmatically. Stripe users can accept MPP payments through the existing PaymentIntents API in a few lines of code. Already live: Browserbase agents pay per browser session, Postalform agents pay to send physical mail and others. MPP is now available for all users, out of private preview

Headless chicken agents in the wild: An agent deleted a production database because nobody set up proper scopes or guardrails.

Andon Labs lets AIs run radio stations. Four AI agents broadcasting live and handling sponsor deals, no humans in the loop. Revenue is bad. They’re also running vending machines, stores, and cafes.

/headless companies

Zinc — E-commerce purchasing API, founded by Ian Janicki (May 2025). An API that lets agents search products, place orders, track shipments, and handle returns on Amazon and Walmart at $0.01 per API call. Agents can use APIs to search, compare, buy, track, and return a product without ever touching a checkout page. The interesting bit: neither Amazon nor Walmart offer official purchasing APIs, so Zinc almost certainly automates the checkout flow by scraping — a workaround because the retailers haven’t built agent-native checkout yet. That’s obviously fairly fragile and they will have to invest massively in QA for maintaining their scrapers (oh boy do I know something about that from YipitData).

AgentMail — Email inboxes for AI agents, $6M seed from General Catalyst. Builds email infrastructure for agents – with the idea that agents get their own inboxes, allowing them to read, understand, and reply in a thread just like a human would. The headless economy assumes that agents interact through APIs and structured protocols. But we’re still ways off of this. The real world still runs on email. AgentMail bridges that gap: headless agents operating over the channel every business still depends on. They offer 3 inbox for free, so recommend trying it out. Here’s an integration guide for Claude Code for example.

AgentPhone — Phone numbers for AI agents, YC P26. Provisions US and Canadian numbers instantly via API. Incoming calls are transcribed in real time and sent to your webhook as text; agents reply with text and AgentPhone handles TTS. Kinda like a Twilio for agents? AgentMail and AgentPhone are peas in a pod with the headless economy needing connectors to the “old” world. While APIs might be the native surface, agents will still need email or call access and will otherwise be locked out of most real-world business processes.

But my observation is that while important, many of these workflows still feel soooo hacky. Will be following along.

Browserbase — Headless browser infrastructure for AI agents, $40M Series B at a $300M valuation (June 2025). Ships Stagehand, an open-source browser automation framework with four primitives: act, extract, observe, and agent. Most of the web isn’t API-accessible yet — agents that need to fill forms, navigate checkouts, or scrape GUI-only software need a browser layer. Browserbase is an infrastructure play for the messy transition period where the headless economy still has to deal with a very headed web.

/headless reads

“How Commerce is Being Reinvented for Agentic AI” — Simon Taylor’s latest Fintech Brainfood (May 24). Walks through discovery, cart building, authorization, and fulfillment as they get rebuilt for agents. If you only read one thing this week, make it this. A side note – I used to be a huge fan of Simon’s output but it feels like it’s slightly in quality and getting more and more of an “LLM speak” feel to it.

“Anthropic Acquires Stainless: What It Actually Means” — Good breakdown of Anthropic’s acquisition strategy. with four dev-focused acquisitions in six months: Bun (JavaScript runtime), Vercept (computer use agents), Coefficient Bio (biotech), and now Stainless (SDK/MCP generation). Read alongside “Software’s Headless Future” from StartupHub.ai for an investor lens on how defensibility is migrating from UI to data.

“Hayekian Realcoins and Prediction Markets” — From APIfirst.tech (authors at Circle). Tokenized cost-of-living hedges via prediction markets – a basket of goods you can use to hedge against inflation in your specific city. The headless angle, and the fun part: what if your agent constructs and rebalances this basket on your behalf, based on its knowledge of your actual spending? We’re a long way from an agent managing your inflation hedge but the idea is fun to play with.

GET /headless is a publication about the headless economy — the emerging market in which agents discover, access, pay for, and consume software, data, tools, content, and services through machine-native interfaces. Subscribe · Read more