# PlaySudoku (remote · mcp.playsudoku.us)

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

- Trust score: 73/100 (medium)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-09-20

## Components

- remote · `mcp.playsudoku.us`: 73/100 (this document), [markdown](https://verifymcp.io/servers/vincentping-playsudoku/mcp.md), [page](https://verifymcp.io/servers/vincentping-playsudoku/mcp)

## Channel facts

- Endpoint: `https://mcp.playsudoku.us/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `1.0.0`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-09-20.

- **Endpoint Security**: 46/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - Authorisation not fully verified: no authorisation is required to call this server, and 4 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe.
  - HTTPS enforcement could not be verified: the plaintext port answered with HTTP 406, which proves neither a plaintext path nor enforcement.
  - HSTS check failed: the Strict-Transport-Security header is absent.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 81/100
  - 100% of prompts and resources have a non-trivial description (not blank, and not just the item's name).
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 996 tokens (~199/item across 5 items; 4 tools + 1 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 87/100
  - Stability observed for 26 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 4 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 5 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.
  - Supports UI / widget rendering.

## Install

### How do I install the PlaySudoku MCP server?

PlaySudoku is a hosted endpoint at https://mcp.playsudoku.us/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add --transport http vincentping-playsudoku 'https://mcp.playsudoku.us/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "vincentping-playsudoku": {
      "url": "https://mcp.playsudoku.us/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "vincentping-playsudoku": {
      "type": "http",
      "url": "https://mcp.playsudoku.us/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.vincentping-playsudoku]
url = "https://mcp.playsudoku.us/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "vincentping-playsudoku": {
      "type": "remote",
      "url": "https://mcp.playsudoku.us/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add vincentping-playsudoku --url 'https://mcp.playsudoku.us/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  vincentping-playsudoku:
    url: "https://mcp.playsudoku.us/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "vincentping-playsudoku": {
      "Transport": "http",
      "Url": "https://mcp.playsudoku.us/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add vincentping-playsudoku -t streamable-http -u 'https://mcp.playsudoku.us/mcp'
```

### Other

```json
{
  "mcpServers": {
    "vincentping-playsudoku": {
      "type": "http",
      "url": "https://mcp.playsudoku.us/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-09-19 (score 73, +1)

No change was recorded against any check on this day. Stability & Change Management went from 80 to 83. That category is still filling its 30-day observation window: 24 days of observed history at the previous scan, 25 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-17 (score 72, +1)

No change was recorded against any check on this day. Stability & Change Management went from 73 to 77. That category is still filling its 30-day observation window: 22 days of observed history at the previous scan, 23 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-15 (score 71, +1)

No change was recorded against any check on this day. Stability & Change Management went from 67 to 70. That category is still filling its 30-day observation window: 20 days of observed history at the previous scan, 21 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-13 (score 70, +1)

No change was recorded against any check on this day. Stability & Change Management went from 60 to 63. That category is still filling its 30-day observation window: 18 days of observed history at the previous scan, 19 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-11 (score 69, +1)

No change was recorded against any check on this day. Stability & Change Management went from 53 to 57. That category is still filling its 30-day observation window: 16 days of observed history at the previous scan, 17 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-08 (score 68, +1)

No change was recorded against any check on this day. Stability & Change Management went from 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-06 (score 67, +1)

No change was recorded against any check on this day. Stability & Change Management went from 37 to 40. That category is still filling its 30-day observation window: 11 days of observed history at the previous scan, 12 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-04 (score 66, +1)

No change was recorded against any check on this day. Stability & Change Management went from 30 to 33. That category is still filling its 30-day observation window: 9 days of observed history at the previous scan, 10 at this one. The score rises as the window fills, whether or not the server changes.

## MCP tools (4)

### `get_sudoku_puzzle` (~276 tokens)

Get 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.

Input parameters:

- `difficulty` (string, required): Puzzle difficulty. Choose based on the user's skill level.
- `technique` (string): Optional technique name to filter by (e.g. "X-Wing", "Hidden Pair", "Naked Triple"). The returned puzzle will require this technique to solve. Omit for a random puzzle of the given difficulty.

### `solve_sudoku` (~169 tokens)

Solve 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.

Input parameters:

- `puzzle` (string, required): 81-character sudoku string. Digits 1–9 for given cells, 0 or . for empty. Whitespace is ignored.

### `explain_next_step` (~378 tokens)

Get 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.

Input parameters:

- `progress` (string): Current board state (81-char string). Clue cells must remain unchanged. Optional — omit to get the very first hint.
- `puzzle` (string, required): Original 81-char sudoku clue string (0 or . for empty cells).

### `check_progress` (~140 tokens)

Check 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.

Input parameters:

- `progress` (string, required): Current 81-char board state to check.
- `puzzle` (string, required): Original 81-char sudoku clue string (0 or . for empty cells).

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/vincentping-playsudoku/mcp#diagnostics

## Score history

- 2026-09-20: 73
- 2026-09-19: 73
- 2026-09-18: 72
- 2026-09-17: 72
- 2026-09-16: 71
- 2026-09-15: 71
- 2026-09-14: 70
- 2026-09-13: 70
- 2026-09-12: 69
- 2026-09-11: 69
- 2026-09-10: 68
- 2026-09-09: 68
- 2026-09-08: 68
- 2026-09-07: 67
- 2026-09-06: 67
- 2026-09-05: 66
- 2026-09-04: 66
- 2026-09-03: 65
- 2026-09-02: 65
- 2026-09-01: 64
- 2026-08-31: 64
- 2026-08-30: 63
- 2026-08-29: 63
- 2026-08-28: 62
- 2026-08-27: 62
- 2026-08-26: 61
- 2026-08-25: 60

## Common questions

### What is the PlaySudoku MCP server?

PlaySudoku is an MCP server listed in the public MCP registry as io.github.vincentping/playsudoku. Deterministic Sudoku puzzles, progress checks, logical hints, and step-by-step solutions. This page covers its hosted endpoint (https://mcp.playsudoku.us/mcp).

### Is the PlaySudoku MCP server safe to use?

PlaySudoku scores 73 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the PlaySudoku MCP server expose?

PlaySudoku exposes 4 tools: get_sudoku_puzzle, solve_sudoku, explain_next_step, check_progress. Their descriptions and schemas cost roughly 963 tokens of context every time the server is loaded.

### Does the PlaySudoku MCP server require authentication?

No. We connected to PlaySudoku without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the PlaySudoku MCP server still maintained?

PlaySudoku is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

## Links

- Remote endpoint: https://mcp.playsudoku.us/mcp
- Changelog RSS feed: https://verifymcp.io/servers/vincentping-playsudoku/mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/vincentping-playsudoku/mcp.json
- HTML version of this page: https://verifymcp.io/servers/vincentping-playsudoku/mcp