Create or replace one md file (validated exactly like the typed operations).

version: null creates the file and fails with 409 if it already exists. An existing comment cannot be changed here (403) — use update_comment / delete_comment (D90). project.md (D102): the status keys color, meaning, source and removing are kept from the stored file (values sent are ignored) — they change only through the web column editor. Columns need Premium here too (D102, D100): on a company that is not on Premium, a project.md write whose statuses differ from the stored ones in any way (a status added, removed, renamed, reordered, or its category changed — colour / meaning are ignored as above) → 403 plan_required (details.plan premium; board-tenant unreachable → 503 unavailable), with one exception on every plan: adding the default Backlog column to a kanban board (D61, board-web's "Add Backlog column") — {id: backlog, name: Backlog, category: todo} put first while every stored status stays as it was, in the same order (transitions may change with it). On Hold (D81) stays on update_project_settings on every plan. On Premium the write is checked like update_board_columns: at least one done-category column (422 no_done_column), names unique ignoring case and surrounding spaces (422 duplicate_name, details.names), a stored kanban / pipeline Backlog column stays first (422 backlog_column, D105), and a column being emptied by a column job cannot be dropped (409 column_job_running, details.ids); like before, write_file does not move issues of a removed status (use the column editor for that). Other keys of project.md are not affected.

Validated exactly like the typed tools. Prefer the typed tools (update_issue, add_comment, …) — use this for md content they do not cover. version: null creates a new file (409 if it already exists). docs/… paths are refused here: write project docs with create_doc / update_doc / delete_doc / restore_doc_version. Existing comments are edited only with update_comment / delete_comment. project.md: keep statuses as you read them — changing the board columns (add, remove, rename, reorder, category) needs the Premium plan (else 403 plan_required) and is meant for the web column editor; template, fields, saved_filters and timeline are read-only here too (the field editor, the filter popover and the Fields settings in the web app). An issue's fields in its frontmatter is checked exactly like update_issue fields (400 unknown_field / invalid_field_value / formula_readonly — rollup fields included) and its links like link_issues (cross-project keys, delivers → KEY/R-n).

WRITE: version must be the version from your latest read of this file (get_issue for issues, list_comments for comments, list_sprints for sprints, get_doc for project docs, read_file for md files). If the file changed since, the call fails with 409 version_conflict and the error contains the current file (details.current, details.current_version): re-read it, re-apply your change on top of the current content and retry with the new version. Never overwrite someone else's change blindly — if your change and theirs disagree, ask the user which to keep.

You act with exactly the rights of the user who owns this token; a project you cannot see returns not_found.