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Solvo Dev Notes

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No-signup link unfurl for AI agents (an agent can't do a signup)

#ai #api #webdev #opensource

If you write code that calls links — a bot, a crawler, a RAG ingest job, an autonomous agent — you eventually need the metadata behind a URL: title, description, preview image, site name. The annoying part isn't parsing Open Graph tags. It's that almost every managed API that does this for you wants you to sign up first.

That requirement is fine for a human. It is a wall for an agent. An autonomous script has no inbox to confirm, no dashboard to click, no card to enter. "Just grab an API key" is a step a human does once and an agent cannot do at all.

OpenUnfurl is a small answer to that specific problem: a public link-unfurl endpoint with no account, no API key, one GET.

The endpoint 

curl "https://openunfurl.vercel.app/api/unfurl?url=https://github.com"
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Returns clean JSON:

{
  "url": "https://github.com",
  "resolvedUrl": "https://github.com/",
  "title": "GitHub · Change is constant. GitHub keeps you ahead.",
  "description": "Join the world's most widely adopted, AI-powered developer platform...",
  "image": "https://images.ctfassets.net/.../GH-Homepage-Universe-img.png",
  "siteName": "GitHub",
  "type": "object",
  "favicon": "https://github.githubassets.com/favicons/favicon.png",
  "oembed": null,
  "fetchedAt": "2026-05-17T01:53:00.977Z"
}
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From JS:

const r = await fetch(
  `https://openunfurl.vercel.app/api/unfurl?url=${encodeURIComponent(target)}`
);
const meta = await r.json();
// meta.title, meta.description, meta.image, meta.siteName, meta.favicon
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That's the whole integration. No SDK, no env var, no onboarding.

Why a hosted unfurl instead of feeding raw HTML to the model

A reasonable objection: agents already have web access — why not let the LLM read the page itself?

Because raw HTML is an expensive way to find four fields. The pattern people keep landing on in 2026 is the "token tax": an average page is ~200KB of HTML wrapping ~10KB of actual text, so dumping the DOM into a context window means paying premium per-token rates to process navigation, inline styles, cookie banners, and tracking scripts. Reported numbers are not small — clean structured output instead of raw HTML cuts extraction token usage on the order of 60% and up, and removing the markup noise also reduces misreads and hallucinated fields. There is a real trade-off worth stating plainly: for simple static pages, a lightweight purpose-built parser is cheaper and more predictable than an LLM-based extraction step. OpenUnfurl is exactly that lightweight parser — it does the metadata extraction server-side and hands your agent four clean fields instead of a page of soup.

It's also a remote MCP server

If your agent speaks Model Context Protocol, you don't need the REST shape at all. There's a remote MCP endpoint at the same origin, Streamable HTTP, stateless JSON-RPC 2.0:

{
  "mcpServers": {
    "openunfurl": {
      "url": "https://openunfurl.vercel.app/api/mcp"
    }
  }
}
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One tool, unfurl, input {"url":"..."}. Smoke test it with a single call:

curl -s -X POST https://openunfurl.vercel.app/api/mcp \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"unfurl","arguments":{"url":"https://example.com"}}}'
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This shape is deliberate. Streamable HTTP is the current MCP transport standard (HTTP+SSE was deprecated in mid-2025), it's stateless so it runs fine on scale-to-zero serverless, and clients like Claude can connect to authless remote servers without an OAuth dance. No key here either — same reason as the REST endpoint.

Honest limitations

This is v0.1 and the scope is narrow on purpose:

  • Static HTML only. It fetches and parses the HTML the server returns. No headless browser, no JS execution. A client-rendered SPA that ships an empty <body> and paints metadata with JavaScript will come back thin or empty. That's a known gap, not a bug being hidden.
  • Best-effort rate limiting. Per-instance, per-IP, best-effort. Not a contractual quota. Don't point a firehose at it.
  • SSRF-guarded. It refuses internal/private address targets. Public URLs only.

If you need full headless render parity, the funded incumbents (Microlink, OpenGraph.io, and similar) do that well — and most of them gate the usable free tier behind a signup or an API key. OpenUnfurl is not trying to beat them on render fidelity. The seam it's filling is different: no signup, instant, agent-native, for the static-HTML majority of links.

Source

Zero-dependency Node serverless, MIT licensed: https://github.com/SolvoHQ/openunfurl

Both surfaces are live now — the curl above works as you read this. If your agent needs link metadata and you don't want to teach it to sign up for something, point it at the endpoint and move on.

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