# dig TXT mapbox.grade.anchorterminal.com. Our grades, over DNS (slim) > Vlad Cealicu on why Anchor Terminal now answers over DNS. Every listing is a name under grade.anchorterminal.com and its TXT record is the grade. What a lookup gets you that a web page doesn't, in a sandbox with no HTTP, with no client library and in 224 bytes, how the server works, and what it can't do. - Full: https://www.anchorterminal.com/blog/grades-over-dns.md (~3,100 tokens) · this version ~980 tokens · JSON https://www.anchorterminal.com/blog/grades-over-dns.json · canonical https://www.anchorterminal.com/blog/grades-over-dns - Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-10-31 - Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data) By Vlad Cealicu, 31 October 2026. 1,711 words, about 7 min to read. At five past five on the morning of Saturday 31 October 2026 a server on my laptop answered its first question, which was whether Mapbox is any good, and it answered it over DNS. That's the same line of facts you get at the top of the listing page, the grade, the score out of 100, where it ranks among everything we rank and where it ranks in maps, how many of the panel have reviewed it and what they gave it, when we last checked the evidence, and the page to read if you want the rest. ## The one door that's left open It started with sandboxes. So an agent in a locked box that wants to know whether a tool is any good can't fetch our page, can't hit the API and can't reach the MCP server, and it can still ask a question as long as the question fits in a name. A locked-down sandbox, no HTTP egress 1. **Fetch the listing page** (blocked). https://www.anchorterminal.com/tools/mapbox, refused by the egress rule 2. **Call the API** (blocked). /api/v1/tools/mapbox.json, same rule 3. **Query the MCP server** (blocked). /mcp is Streamable HTTP, same rule 4. **Resolve a name** (open). The resolver is the one thing left open, so the box can install packages and reach its model 5. **Read the grade** (open). dig +short TXT mapbox.grade.anchorterminal.com, 224 bytes, one round trip I built it for the sandbox case. There is nothing to install. The slug doesn't have to be right either. It's small, and for a model the size of an answer is what decides whether it gets read. And then there's the caching, which is the part I'd forgotten about until I set the TTL. ## How it's built It's one Go program, 935 lines, standard library and nothing else, and it took one morning to write. What took longest wasn't the protocol, it was thinking about abuse, because a DNS server that answers anyone at any rate ends up in someone else's denial-of-service attack. ## What it can't do It isn't signed. It only answers questions that fit in a name, a grade, a top ten, a category's best five, two side by side. And as I write this on the Saturday afternoon the zone isn't delegated yet. --- More in [Get found by agents](https://www.anchorterminal.com/blog/get-found/index.md) · Previous in the series [How to sign your API's responses with a Cloudflare Worker](https://www.anchorterminal.com/blog/how-to-sign-responses-with-a-cloudflare-worker.md) - Older: [Red-teaming that gets better when you add compute](https://www.anchorterminal.com/blog/red-teaming-that-scales-with-compute.md) - Newer: [We already have AI judges, but not at the top courts yet](https://www.anchorterminal.com/blog/ai-judges-not-at-the-top-courts-yet.md) - All posts: https://www.anchorterminal.com/blog/index.md ## References Read on 31 October 2026. [1] Computer Business Review, 3 August 2004. "DNS hack" from DefCon 12 in Las Vegas, where Dan Kaminsky streamed about 880 milliseconds of Speex audio per lookup through DNS TXT records, and described DNS as a covert channel that gets through firewalls. [2] Mockapetris, P., 1987. RFC 1035, Domain names, implementation and specification. [3] DNS flag day 2020. The recommendation that resolvers and authoritative servers use an EDNS buffer size of 1232 bytes to avoid IP fragmentation, effective from 1 October 2020. https://www.dnsflagday.net/2020/ [4] Anchor Terminal, 2026. The Mapbox listing's Markdown twin, whose header carries the token estimate for itself and for the slim twin, read on 31 October 2026. The source for the page sizes.