PlaySudoku

Deterministic Sudoku puzzles, progress checks, logical hints, and step-by-step solutions.

CommunityDegradedNo sign-inGlobalFreeRead-only

What it can do

    What data it sees

    Do you need an account

    No: the server works without sign-in

    Deterministic Sudoku puzzles, progress checks, logical hints, and step-by-step solutions.

    How to connect

    How to connect PlaySudoku to Claude

    The server address to paste into Claude settings:

    https://mcp.playsudoku.us/mcp

    1. Open Claude (claude.ai or the desktop app).
    2. Go to Settings → Connectors.
    3. Click Add custom connector.
    4. Paste the server address copied below into Remote MCP server URL and click Add.
    5. In a chat, click + → Connectors and switch the new connector on.

    Custom connectors are available on Free, Pro, Max, Team and Enterprise plans (Free is limited to one). On Team and Enterprise an organization Owner adds the connector first under Organization settings → Connectors.

    Authorization

    After you click Add, a sign-in window for the service opens. Sign in with your own account and approve access. Claude never sees your password.

    How to connect PlaySudoku to ChatGPT

    The server address to paste into ChatGPT settings:

    https://mcp.playsudoku.us/mcp

    1. Open ChatGPT in a browser (chatgpt.com). A Plus, Pro, Business, Enterprise or Edu plan is required.
    2. Turn on developer mode once: Settings → Apps → Advanced settings → Developer mode.
    3. Open Settings → Connectors and click Create.
    4. Fill in the form: Name (anything), Description (one line about what the service does), MCP server URL (copy it below).
    5. Under Authentication choose OAuth if the service requires sign-in, otherwise None. Click Create.
    6. In a new chat open + → Apps/Connectors and enable the connector.

    OpenAI has renamed this section before (Connectors → Apps/Plugins). If the label differs, search settings for "developer mode". On Business/Enterprise workspaces an admin must allow custom connectors first.

    Authorization

    On first use ChatGPT opens the service's sign-in window. Sign in and approve access.

    How to connect PlaySudoku to Cursor

    The server address to paste into Cursor settings:

    https://mcp.playsudoku.us/mcp

    Fastest: click Open in Cursor below and confirm the prompt.

    Manually:

    1. In Cursor open Settings → Cursor Settings → MCP and click Add new global MCP server.
    2. Paste the JSON copied below into ~/.cursor/mcp.json (per project: .cursor/mcp.json in the repo root).
    3. Save the file. The server appears in the MCP list; authorize it there if asked.

    Authorization

    If the service needs sign-in, an authorize button appears next to the server in the MCP list.

    Server tool list (4)

    Raw names from tools/list. Only developers need these.

    get_sudoku_puzzleGet a random sudoku puzzle from the PlaySudoku.us collection. Puzzle is returned as an 81-character string: digits 1–9 for given cells, 0 for empty cells. The response includes the techniques required to solve the puzzle and a solve_url to the interactive solver. Difficulties: easy (30–38 givens), medium (44–50), hard (50–55), expert (56–62), evil (56–62). Optional: pass a technique name (e.g. "X-Wing", "Hidden Pair") to get a puzzle that specifically requires that technique — useful when the user wants to practice a particular solving method. If no puzzle at the requested difficulty uses that technique, the error message lists which difficulties do have it. Use solve_sudoku for a full step-by-step solution, or explain_next_step to get one hint at a time. Every response includes a solve_url where the same puzzle can be continued in the interactive solver.
    solve_sudokuSolve a sudoku puzzle completely with step-by-step logical deduction. Input: 81-character string of digits (0 or . for empty cells). Whitespace is tolerated. Returns: every solving step with technique name + human-readable explanation + action, the final solution string, a technique summary (counts), and tutorial links. Only uses logical techniques — never guesses. If the puzzle cannot be solved logically, the steps will end before completion. Use this when the user wants to understand how to solve a puzzle from scratch. The response includes a solve_url for continuing the same board interactively and tutorial_links for techniques used in the solution.
    explain_next_stepGet the next logical solving step for a sudoku puzzle, optionally from a partially-filled state. TWO-BOARD MODE (puzzle + progress) — use when you know both the original clue grid and the user's current work: puzzle: the original 81-char clue string (the given digits only, 0/. for empty cells). progress: the user's current 81-char board — must keep all original clue digits in place. This mode detects incorrect entries: if any user-filled cell contradicts the solution, the tool returns incorrect_cells instead of a step hint, so the user can correct errors before continuing. Use this when the user is solving a puzzle they received from get_sudoku_puzzle (puzzle is known). SINGLE-BOARD MODE (puzzle only, no progress) — use when the original clue grid is unknown (e.g. photo OCR): Pass the user's current full board as puzzle with no progress argument. The tool treats the board as both the clue grid and the current state, so it will not perform error checking (it cannot distinguish given digits from user entries). It simply returns the next logical step. Use this when you cannot separate the original clues from the user's entries. Returns: { technique, explanation, action, tutorial_links } on success, or { incorrect_cells, message } if errors found. Use this for step-by-step coaching — one hint at a time. Every response includes a solve_url for continuing the same board interactively and, on success, tutorial_links for the named technique.
    check_progressCheck a user's current progress against the correct solution. Returns factual information only: whether the puzzle is complete, whether all filled cells are correct, which cells are incorrect (with the entered digit), and how many cells remain empty. Does not give hints or coaching — use explain_next_step for that. Use this when the user asks "am I done?" or "did I make any mistakes?" Every response includes a solve_url where the same puzzle can be continued in the interactive solver.