Create a new board

Initial board content applied atomically at create time (POST /api/boards content field / MCP create_board). The combined input arrays may contain at most 2550 entries (counted exactly as supplied — entries are never merged); template-seeded columns do not count as input. The D1 batch is capped at 320 statements (multi-row INSERTs sized against D1's 100-bound-parameters-per-statement limit). In practice the 5 MB request-body cap bites first on image-heavy imports, well before 2550 entries.

Per-item author. Every item in texts / lines / images / columns / tasks / lanes accepts an optional author (1–80 chars of [A-Za-z0-9:_\-.], trimmed — the same rule as the REST/WS paths). Absent or null inherits the body-level author (default ai:import); an invalid value is 400 {error:"invalid_item", kind, index, reason}. This exists because an item's author is its CREATOR and is never rewritten, so restoring someone else's board must be able to carry the original authorship instead of stamping everything as the importer.

sourceId (texts and images). Optional string, 1–128 chars, unique across the whole import. WRITE-ONLY: it is never stored and never becomes the row id — item ids are always server-minted and returned in the response's ids. Its only effect is anchor resolution: a lines[i].anchors.start.id / .end.id matching a declared sourceId is rewritten to that item's minted id. An anchor id matching nothing is left verbatim and renders as a free stroke end.

Strict value checks. tasks[].done must be a real boolean (or null/omitted); a truthy stand-in like "false" is 400 {error:"invalid_item", kind:"tasks", index, reason} rather than being coerced into a COMPLETED card. lanes may name each lane index at most once; a second entry for the same index is 400 {error:"invalid_item", kind:"lanes", index, reason} on that second entry, since collapsing it would overwrite the first entry's author.

Draw kinds (texts/lines/images) require draw mode; kanban kinds (columns/tasks/lanes/colWidth) require mode: "todo" — a mismatch is 400 content_mode_mismatch. All standard per-board quotas also apply (live values in /quotas.json).

Todo boards only: the created columns (from content.columns, or the template seed).

Present whenever content was provided (even all-zero) — the feature-detection signal for board import. Per-kind counts of rows created FROM content; template-seeded columns are NOT counted.

Present whenever content was provided, alongside imported. The server-minted ids for the imported rows: index i of each array is the id created for content.<kind>[i], in the order the caller supplied them. Item ids are ALWAYS minted server-side — a caller may not choose them (ids are globally unique and the item write paths upsert on id, so an honoured caller id could overwrite rows on another board). columns is [] when the columns came from the template seed (those are already returned in full in columns). There is no lanes array — lane rows have no synthetic id, they are keyed by (board_id, lane).