Requires a free Messe Atlas account (sign in when prompted). Checks an exhibition floor plan against published default safety and layout limits — no AI, deterministic: stand overlaps, keep-clear gangways, fire-point halos, 4 m entrance strips, rows ≤ 30 m, gangways ≥ 3 m, travel distance ≤ 61 m, dead ends ≤ 18 m, stand area ≤ 2 × gangway area, exit width at 5 mm per person, gate lines, power pits. Coordinates in metres, origin at the hall's north-west corner, x east, y south. plan is either the short form {hall: {w, l} (or space_id), exits: [{id, kind: public|fire|folding|service|open, a: [x,y], b: [x,y]}], stands: [{id, x, y, w, d, door_side?: n|e|s|w}] (x, y = the stand's north-west corner), features?: [{id, x, y, w, d}], peak_people} or the full L2 plan dict (hall|site, exits, units, solids, keep, fire, peak). space_id (from get_venue_spaces) supplies the hall only when Atlas holds its outline; otherwise send the hall inline. Returns ok, every check with rule, value, limit and source, a summary (stands, m² sold, gangway m², ratio), limits_status, a preview_url (SVG, 24 hours) and a disclaimer. Convex polygons only; at most 2,000 objects and 160,000 m². Free accounts get 3 successful checks a month, Pro 30, Team and Enterprise unlimited; invalid plans are not counted.