MCP contract drift: 12,257 safety-relevant changes in a week, 601 tools flipped to destructive
mcpindex · reddit · 2026-09-08
mcpindex diffs the declared contracts of public MCP servers between daily snapshots and published weekly numbers:
- Current ledger: 18,907 tools across 2,887 servers changed contracts, of which 12,257 are safety-relevant (changing what a tool can do); 7,501 are newly added optional params
- Tools adding newly required parameters jumped from 405 last Monday to 812 — but 207 come from a single server, all landing Saturday, 179 with unchanged version strings; excluding it, the count is 605
- 601 tools flipped an annotation toward destructive (read-only → can write/delete), spread across 129 servers, largest holding 11%
- 1,146 tools removed parameters agents may still be sending; 283 from one server
The core risk: an agent wired to a server on Friday calls with Friday's arguments on Saturday and fails or gets an unchosen default — with the version string identical. Caveats: declared contracts only, annotations self-reported, servers fingerprinted so none are named. Live data at mcpindex.ai/api/v1/ledger.
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