{
 "slug": "tool-parameter-changes",
 "url": "https://stillosdigitalholdings.com/findings/tool-parameter-changes",
 "question": "When an MCP tool keeps its name but quietly changes the parameters it accepts, does anything signal it?",
 "headline": "3,386 observed MCP parameter changes — and 73.6% carried no version change.",
 "cite_as": "73.6% of MCP tool-parameter changes carry no version change (Still OS Digital Holdings LLC, Surface History, n=3,386 parameter changes across 1,421 hosts, 2026-09-21 to 2026-10-30).",
 "numbers": {
  "Parameter changes observed": "3,386",
  "Of those, no version change": "2,493 (73.6%)",
  "Distinct hosts": "1,421",
  "Tool-surface changes, same window": "6,384",
  "Description-only changes, same window": "29,077",
  "Observation window": "2026-09-21 → 2026-10-30"
 },
 "method": "Each server's live tool definitions are fetched on a repeating cadence; a change to a retained tool's input parameters with no change to its name is recorded as PARAMS_CHANGED, separately from tools added/removed (SURFACE_CHANGED) and description-only edits. Event-sourced and replayable to any past date.",
 "producers": [
  "/home/marcus/state/mcp-census/surface-clock/surface-events.jsonl"
 ]
}