mcpindex Source Liveness — Baseline v1: a corroborated, timestamp-anchored census of source reachability in the Model Context Protocol registry

A corroborated, timestamp-anchored census of whether the source code behind every server in the official Model Context Protocol (MCP) registry is still publicly reachable, measured on 2026-07-20. Finding: of 13,105 distinct GitHub repositories referenced by the 17,673 registry servers, 1,830 (14.0%) were not publicly accessible as of the census, affecting 2,069 listed servers. What is gone is the ability to audit the source before an autonomous agent invokes the tool. This census measured URL reachability only and makes no claim about whether a package still installs. Method: every repository was checked from two independent vantages (authenticated GitHub API from datacenter egress; unauthenticated web UI from residential egress) that differ on network, method, and authentication. Only URLs both vantages agreed were unreachable are reported; across all 1,830 there were zero cross-vantage disagreements. A URL is confirmed only after two failed checks at least 48 hours apart. The census sweep's store digest is anchored to the Bitcoin blockchain via OpenTimestamps; the proof is included and independently verifiable. Methodological contribution: anonymous git ls-remote against a deleted or private GitHub repository returns a 401 credential prompt rather than a 404, so a checker that trusts anonymous git alone reports zero casualties while appearing healthy. This masked all 1,830 unreachable repositories in the first two passes; only an authenticated corroboration leg surfaced them. Any at-scale repository-liveness study must account for this. Limitations (see LIMITATIONS.md): a GitHub 404 cannot distinguish a deleted repository from a deliberately private one; both vantages read the same registry-supplied URL, so a stale URL whose source moved elsewhere is a residual false-positive class only a maintainer can catch; and this is a baseline, so unreachability is asserted as of the census date, not death dates. Live counterpart: https://mcpindex.ai/research/source-liveness