Four tools with Japanese descriptions and basic schemas. All tools have input schemas and descriptions present, but descriptions are terse (avg ~60 chars, well below the 194-char baseline). Parameter descriptions are minimal or absent. No error handling guidance, no recovery paths, and no output schema documentation visible. Tools lack English descriptions, limiting accessibility. Schemas use Zod but lack detailed type constraints and validation rules in descriptions. No tool annotations (readOnlyHint/destructiveHint/idempotent). Naming is verb-based but generic (start_, sync_, reset_, draw_) without clear domain context.

• Expand all descriptions to 100 - 200 characters. Include WHAT (e.g. 'Draws the next number from the remaining pool'), WHEN (e.g. 'Call after user says "draw next"'), and WHAT IT RETURNS (e.g. 'Returns updated card state and a message indicating if the number was on the card, or if bingo/reach was achieved'). Example: 'draw_number: Draws one number from the remaining pool and auto-marks it on the card if present. Returns the updated card state and a message describing the result (hit/miss/reach/bingo). Call when the user requests the next number. Non-idempotent, each call advances the game state.'
• Document output schemas formally in each tool definition. Add an outputSchema field (or equivalent in your framework) that describes the GameState structure: {remain: number[], history: number[], card: Cell[][], bingoLines?: Line[], reachLines?: Line[]}. This enables LLMs to extract and chain results.
• Add parameter descriptions for 'state' in sync_state. Specify: 'Game state object with remain (array of undrawn numbers), history (array of drawn numbers in order), and card (5x5 grid of cells with value and marked flag). All fields required.'
• Add tool annotations: mark all four tools with destructiveHint: true (they modify game state) and idempotentHint: false (repeated calls produce different results). This signals to LLMs that retries are unsafe and state changes are irreversible.
• Add error handling and recovery guidance. When draw_number detects remain.length === 0, return: {error: 'No numbers remaining. Game is complete. Call reset_game() to start a new game or start_bingo(mode="resume") to continue.'}. Classify errors as retryable (network) vs user-fixable (invalid input) vs fatal (game over).