Chess Position Analyzer

Creates or updates an interactive chessboard for visualizing and manipulating chess positions, using FEN if provided or the standard starting position otherwise. Use this when the user wants to view, set up, edit, or discuss a chess position. IMPORTANT behavior — read carefully: - After the board is opened, the user may freely drag pieces on the widget (sandbox mode — arbitrary edits are allowed). - The current live board position is stored in `widgetState.fen`. The widget also persists `widgetState.orientation`, `widgetState.sideToMove`, `widgetState.ascii` (a pre-rendered 8x8 grid of the board, with rank labels on the left and file labels at the bottom), and `widgetState.pieces` (a map of color -> role -> list of squares). Prefer reading `widgetState.ascii` or `widgetState.pieces` directly when you need to enumerate what is on the board — LLMs are error-prone at FEN parsing, so the pre-decoded fields are authoritative. - For ANY later reasoning about the board — current position, last move, legal ideas, opening name, material count, check/checkmate status, whose turn it is, or anything else about the board as it exists now — ALWAYS read `widgetState.fen`. Do NOT rely on the `fen` returned in this tool's initial structuredContent; it reflects only the position at load time and becomes stale the moment the user interacts with the widget. - Before answering any board-state question, first inspect `widgetState.fen`. Do not call this tool again just to read the current position. - Only call this tool again when you need to open the board, reset it, load a specific FEN, or change orientation. - If `widgetState.fen` differs from the originally loaded FEN, treat that difference as user-made board edits or moves. Because sandbox mode allows arbitrary piece dragging, avoid claiming the position arose from legal play unless the moves are explicitly inferable and legal. For reasoning, prefer `widgetState.fen` over the tool-returned `fen` every time. Example: - Tool opens board with the starting position. - User drags pieces to play 1.e4 e5 2.Qf3. - The tool's originally returned `fen` is still the starting position. - The correct current position must be read from `widgetState.fen`.