Four AI agents re-checked the guides

Turva.dev deployed four AI agents running Claude Fable 5 to re-check specification claims in its guides against primary sources, finding one high-severity issue in the MCP guide where the SEP-2127 proposal had moved, and a medium finding where an IETF RateLimit header draft expired. Two machine-readable profiles (UCP and MPP) had drifted from their specifications, passing scans despite using invalid keys. The site now anchors claims with dates and schedules re-checks for fast-moving families.

The guides on turva.dev describe other people's specifications, and specifications move. A sentence that says "the specification says" is true the day it ships and starts aging the day after, and no scanner will tell you when it has gone stale. So the four AI agents that read the site line by line https://turva.dev/blog/auditing-the-auditor came back for a second pass, all running Claude Fable 5, each taking one family of standards: the agent commerce stack, MCP discovery, the discovery files from agents.json to llms.txt, and the plumbing of authentication and response headers. Their job was to re-read every specification claim in those guides against the primary source behind it. The pass came back with one finding rated high, one medium and six small. The high one sat in the MCP guide. It described the server card proposal, SEP-2127, in the present tense, and the proposal had moved. As of July 2026 it sits on MCP's extensions track as an experimental extension, and the current draft recommends serving the card relative to the server's endpoint plus a catalog at /.well-known/mcp/catalog.json. Nothing in the old sentence was wrong when it was written. It stayed still while the proposal moved. The medium finding was quieter. The response-header guide leaned on the IETF draft for standard RateLimit headers, and that draft expired in March 2026 without a successor. The six small ones were wording: vocabulary that predated A2A 1.0, stale lines about the Open Knowledge Format, a Cache-Control nuance, and one phrase about ai-catalog.json contributors that had aged in two places at once, because a blog post had quoted the guide. Two of the machine-readable profiles turva.dev serves had drifted from their own specifications, and that is a harder failure than stale prose, because these files exist for software and both had passed every scan since they shipped. The UCP profile used service keys in a namespace the specification reserves for its own governing body, and listed transports its enum does not contain. The MPP manifest declared a version field the protocol does not define. A scanner checks that a profile exists and parses. It does not check that the vocabulary inside it exists in the specification, so an invented key passes as easily as a real one. Both profiles are now in the specification's own shape, verified against the primary text and validated programmatically, and both scanners stayed green through the change. The honest form cost nothing. Both scanners were re-run after the fixes. startuphub.ai reads 100/100 with grade A+ and isitagentready.com reads Level 5, the same result as before the pass. The scores did not move in either direction, and that is worth pausing on. A score measures the shape of a site at scan time, and the currency of a sentence about somebody else's specification is outside every scanner's reach. If reading every line is part of the promise, somebody has to re-read the lines after the world moves. The lasting repair is anchoring. A guide claim about a moving specification now carries its date, as of July 2026, so when the specification moves again the sentence stays true as a dated statement instead of quietly turning false. The families that move fastest, agent commerce and MCP discovery, go back on a re-check schedule, because this pass showed the drift interval there is a matter of weeks. For an audit that reads your agent-facing claims against the specifications they cite, contact info@turva.dev mailto:info@turva.dev . Originally published at https://turva.dev/blog/re-checking-the-guides