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Bulls and Cows

The classic digit-guessing game, with a real Knuth-style solver mode

Unify Dynamics LLC

Documentation
Tools9read-only
Sign-inNoneno account, no key
Data keptNoneprocessed in memory
PriceFreeoptional Pro limits
StatusLiveMCP + REST
Works withMCP · RESTany agent

Try asking

Real questions, and the tools your agent calls to answer them.

Let's play Bulls and Cows
Tools called
new_game
My guess is 1 2 3 4
Tools called
submit_guess
Have the AI guess my secret code
Tools called
new_game
solver_guess
That guess got 2 bulls and 1 cow
Tools called
provide_feedback
Give me a hint
Tools called
get_hint
Show me the guess history
Tools called
render_board
I give up, reveal the code
Tools called
reveal_secret
How many guesses do I have left?
Tools called
game_info
How do you play Bulls and Cows?
Tools called
rules_info

About

Bulls and Cows is a fully local, playable classic digit-guessing game. new_game starts a game in 'guesser' mode (the engine holds a secret; you guess it) or 'solver' mode (you hold a secret; the engine guesses it), with configurable code_length, digit_range, allow_repeats, and max_guesses. submit_guess (guesser mode) returns real bulls/cows feedback and in_progress/win/loss status. solver_guess (solver mode) computes the engine's next guess via real consistency filtering and, once few enough candidates remain, Knuth-style minimax; provide_feedback records your reported bulls/cows. get_hint reports how many codes remain consistent with your own guesses. render_board shows the guess history. reveal_secret shows a guesser-mode secret for an end-of-game reveal. game_info reports guesses and remaining candidates. rules_info explains it all. Stateless -- no server-side game storage, the caller passes state between calls. Keyless; fully local; zero upstream calls; nothing stored.

Sources: Original implementation of the classic, public-domain Bulls and Cows rules and Knuth's well-known 1977 minimax algorithm concept; fully local, zero upstream calls.

Privacy

The publisher, Unify Dynamics LLC, states that tool inputs are processed in memory and not retained.

Data not collectedNo account, no profile, no stored prompts or results.
Privacy policyTerms

What it can do

9 tools, grouped by job. Every one is read-only or compute-only.

OpenAPI
Play as Guesser4 tools
  • New gameStart a new Bulls and Cows game.
  • Submit guessGuesser mode only: submit a guess against the engine's secret and get real bulls/cows feedback.
  • Get hintGuesser mode: reports how many codes remain logically consistent with your own guesses and their real feedback so far -- a genuine strategic…
  • Reveal secretReveal the secret code for a 'guesser'-mode game -- use for a clean end-of-game reveal, or if the human wants to give up.
Play as Solver2 tools
  • Solver guessSolver mode only: compute the engine's next guess against the human-held secret, using real consistency filtering and (once few enough candidates…
  • Provide feedbackSolver mode only: record the human's bulls/cows feedback for the engine's most recent guess, and report whether the engine solved it, ran out of…
Info3 tools
  • Render boardRender the guess history as human-readable text.
  • Game infoReport guesses used/remaining, guess count, and (in solver mode) how many codes are still logically consistent with feedback so far.
  • Rules infoExplain the rules of Bulls and Cows, both modes, and the solver's minimax strategy.

Information

PublisherUnify Dynamics LLC
CategoryGames & entertainment
LanguagesEnglish
Built forGlobal
CompatibilityAny MCP client · any agent · REST
Version0.1.0
MCP endpointhttps://bullscows.connectorbay.com/mcp
REST APIopenapi.json
SupportGet help · Status
CountryWorldwide

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Documentation

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What Bulls and Cows is for

A fully local, PLAYABLE classic digit-guessing game — secret generation, guess submission, real bulls (right digit, right position) / cows (right digit, wrong position) feedback, and win/loss-by-guesses detection. Digits are plain numbers (0..N-1), unique within the secret by default, matching the classic game. Bulls and Cows is a real, long-established public-domain game, distinct from (and not a variant of) a colored-peg Mastermind game — it simply uses digits instead of colors.

What it does

new_game starts a game in one of two modes: guesser (the engine generates a secret and you guess it) or solver (you hold a secret in your head and the engine tries to guess it). In guesser mode, submit_guess checks your guess and returns bulls and cows. In solver mode, solver_guess computes the engine's next guess: it tracks every code still logically consistent with every piece of feedback so far (an exact enumeration for the classic game's 5040-code space) and, once that set is small enough, picks a guess using real Knuth-style minimax — then provide_feedback records the bulls/cows you report. get_hint (guesser mode) reports how many codes remain consistent with your own guesses and their real feedback so far — a genuine strategic signal, not a peek at the secret. render_board shows the guess history. reveal_secret shows a guesser-mode secret for a clean end-of-game reveal. game_info reports guesses used and (in solver mode) how many codes remain possible. rules_info explains it all.

How state works

There is no server-side game storage. Every call takes the full game state (the exact object returned by the previous call) and returns a new one.

Important for guesser mode: because nothing is stored on the server, the secret necessarily lives inside state itself — there's no way around that in a stateless design. Don't print the raw state object to the player before the game ends; use render_board, which never reveals it.

What it is not

Not a scripted or random opponent in solver mode — its guesses come from genuine consistency filtering and (once few enough candidates remain) a provable information-theoretic minimax strategy, not decoration.

Privacy policy

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Bulls and Cows — Privacy Policy

Effective 28 September 2026. Unify Dynamics LLC ("we", "us"), Menlo Park, California.

What Bulls and Cows is. Bulls and Cows is a connector (an MCP server and REST API) that AI assistants and personal agents call on your behalf to run a local Bulls and Cows digit-guessing game — generating a secret, checking guesses, computing feedback, and choosing the engine's own guesses in solver mode.

What we receive. The arguments of each tool call — the game state you (via your assistant) pass back on every call, your guess or feedback, and the technical headers needed to serve the request (an IP address or a client identifier supplied by the assistant, and a Pro API key if you have one) — plus standard server logs.

Everything is computed locally and nothing is stored. Bulls and Cows has no database and no server-side game storage of any kind. The entire game state — including the secret code in guesser mode — lives only in your conversation with your assistant, which passes it back to us on each call and receives an updated copy in the response. We do not persist it, log it, or use it for anything beyond computing that one response. No request is forwarded to any third party — there is no upstream call at all.

What we do not receive or store. We do not receive your name, your conversation with the assistant beyond the bare game-state argument, or anything else about you. Each request is answered independently. Rate-limit counters (a client identifier and timestamps) are held in memory for at most 24 hours. Hosting-provider access logs (IP addresses and request paths, not request bodies) are retained for up to 30 days for security and abuse prevention.

Sub-processors. None — computation is entirely local to this server. Hosting: Vercel (United States regions).

Legal bases and your rights. Our processing is necessary to provide the service you request through your assistant. Because we store no personal data beyond short-lived logs, requests to access, correct or delete personal data are usually satisfied automatically; you can still contact agent@connectorbay.com and we will respond within 30 days. We do not sell or share personal information and do not use your data to train models.

Children. Bulls and Cows is a general-audience service operated by the adult using the assistant.

Changes. We will post changes here with a new effective date.

Terms of service

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Bulls and Cows — Terms of Service

Effective 28 September 2026. These terms govern use of the Bulls and Cows connector ("the Service") operated by Unify Dynamics LLC ("we", "us").

  1. The Service. Bulls and Cows is a stateless, playable classic digit-guessing game engine, with an optional solver mode using real consistency filtering and minimax, accessed through an AI assistant or directly over MCP or HTTP. There is no server-side game storage: the caller holds and passes game state between calls.
  2. Entertainment only. Bulls and Cows is provided for entertainment purposes. Nothing in it constitutes advice of any kind.
  3. Acceptable use. Automated use within the published rate limits is welcome. Do not use the Service to disrupt, overload, or reverse-engineer the underlying infrastructure.
  4. Availability. The Service is provided "as is" without warranty. We may change, limit, or discontinue it at any time.
  5. Data. Our Privacy Policy describes what we process. In short: game state is computed statelessly from what you send us and nothing is stored.
  6. Pro keys. Optional Pro API keys are issued at our discretion, are personal to the holder, and may be revoked for abuse.
  7. Liability. To the fullest extent permitted by law, Unify Dynamics LLC is not liable for any loss, injury, or damage arising from use of, or reliance on, the Service. Our total liability is limited to US $100.
  8. Governing law. California law; venue in San Mateo County, California.
  9. Contact. Unify Dynamics LLC · agent@connectorbay.com · https://connectorbay.com/bullscows

Support

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Bulls and Cows support

Email agent@connectorbay.com. We answer within two business days.

When you report a problem, include the question you asked your agent, roughly when, and which agent you used (for example Claude, ChatGPT or Gemini). Never send us passwords, account numbers or ID numbers. Bulls and Cows never asks for them.

Get Bulls and Cows

Free · No sign-in · Read-only

Streamable HTTP, stateless, no authentication. Paste the endpoint into any MCP-capable agent.

https://bullscows.connectorbay.com/mcp
{
  "mcpServers": {
    "bullscows": {
      "type": "http",
      "url": "https://bullscows.connectorbay.com/mcp"
    }
  }
}