Spec Driven Development
by formulahendry
MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.
Runs on your computer★ 440MITUpdated 14 months ago
Install
MythxEngine
Overview
Description from the maker (original English)
Tabletop RPG engine over MCP: dice, combat, stress, clocks, world generation, four bundled worlds
PopNx MCP’s three pillars
These three are never merged into one score: opinions, measurements and popularity are different things.
- User voiceiNo reviews yetReviews open together with accounts in a later step
- Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
- UsageiNot measured yet★ –
What you can do with it
We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.
- Connection: Runs on your computer
- Transport: stdio
- Category: Other
Install
Pick the AI app you use, then copy the settings.
Before you install
- Basic checks: 1 of 1 passed
- Runs on your computer with your user’s permissions (files, network, apps).
- You fill in yourself:
RPG_MCP_DATA_DIR
You need
- npmNode.js installed (for the npx command)
Which app do you use?
Pick your app above. We remember it, so next time the button says “Install in …”.
Download the maker’s .mcpb file
The link goes to the maker’s own file; we do not host or repackage it. Open the file and Claude Desktop installs it.
Run this in your terminal
claude mcp add mythxengine --env RPG_MCP_DATA_DIR=your-value -- npx -y @mythxengine/mcp-serverFill in the empty values before running it.
Or copy the settings yourself
Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json
{
"mcpServers": {
"mythxengine": {
"command": "npx",
"args": [
"-y",
"@mythxengine/mcp-server"
],
"env": {
"RPG_MCP_DATA_DIR": "your-value"
}
}
}
}Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.
Or copy the settings yourself
Paste into .vscode/mcp.json in your project
{
"servers": {
"mythxengine": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"@mythxengine/mcp-server"
],
"env": {
"RPG_MCP_DATA_DIR": "your-value"
}
}
}
}Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.
This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.
Your choice stays on this device in a cookie; no account needed.
Values you fill in
RPG_MCP_DATA_DIRenvWhere sessions and world packs are stored (default: ~/.mythxengine/data)
These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.
What it can do
Runs on your computer; the tool list appears in your AI app after you install it.
Basic checksi
We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 7, 2026
- ✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account protoLabsAI, which owns the repo
- … Not checked yet
Still maintained
We have not read this repo from GitHub yet
- … Not checked yet
Has a licence
We have not read this repo from GitHub yet
- – Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
- – Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
- … Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints
Compared with others in Otheri
- More stars than 0% of the other 32558 servers in this category
- Published to the registry more recently than 17% of the other 32558 servers in this category
- Basic checks equal to or better than 100% of the other 32558 servers in this category
Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.
Common questions
Is MythxEngine safe?
It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.
What keys or codes does it need?
The registry does not list a required key, though some servers ask you to sign in on first use.
Does it run on my computer or in the cloud?
It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).
Is it still maintained?
The GitHub repo last changed –, and the latest version (0.3.0) reached the registry 4 months ago.
Which apps can use it?
Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need Node.js, MCPB on your computer.
What can I use instead?
In the same category: Spec Driven Development, Remote Desktop Commander, FactLot
Alternatives
Servers in the same category from other makers, sorted by stars.
Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi
Remote Desktop Commander
by desktop-commander
Remote Desktop Commander: use files, terminal and processes on your own computers from any AI app.
Runs in the cloud★ 211Updated yesterday
Install
FactLot
by 9mp96ygnbk-alt
Cited CRE facts and deterministic calculators for agents: rent, CAM, debt sizing, IRR, parcel IDs.
Computer or cloudUpdated today
Install
README from the maker
Open the README
Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.
MythxEngine — tabletop RPG engine over MCP
A complete tabletop RPG engine your AI can run: deterministic dice, five-tier outcomes, FitD-style stress, combat tracking, situation clocks, investigations, NPC relationships, world generation — 134 tools over the Model Context Protocol, with four complete starter worlds bundled in.
Claude (or any MCP client) becomes your Game Master. The engine keeps the rules honest: same seed + same actions = same outcome.
Install
Claude Code — plugin (skills + tools, recommended)
/plugin marketplace add protoLabsAI/mythx-mcp/plugin install rpg@mythx-plugins
One install delivers the MCP server plus play skills (/rpg:play, /rpg:combat-mode, /rpg:world-building-mode, …).
Claude Code — tools only
claude mcp add rpg -- npx -y @mythxengine/mcp-serverRequires Node >= 22.13.
Claude Desktop
Download mythxengine- .mcpb from the latest release and drag it into Settings → Extensions. No other setup — Claude Desktop ships its own Node runtime.
Five-minute walkthrough
Everything below is one conversation with Claude after installing. Four worlds are imported on first run — Port Miriam (harbor noir), Aethelgard (mythic frontier), Threshold Deep (weird depths), and the Treehouse Anthology.
1. Pick a world, make a character.
Start a session in Port Miriam. I want to play a dockside fixer who owes the
wrong people money.
The GM calls create_session, load_world_summary, and create_character — your fixer gets HP, stress, gear, and a spot in the world's faction web.
2. Roll with real stakes. Every test is framed with position (how bad is failure?) and effect (how much does success buy?):
I try to slip past the harbor patrol to reach the smuggler's skiff.
roll_test → risky position / standard effect → 11 vs 13: partial"Yes, but..." — you reach the skiff, and a lantern swings your way. GM move suggested: put_someone_in_spot
Five outcomes — critical success, success, partial, failure, critical failure — and on a bad roll you can push_roll (spend 2 stress for +1d6) or resist_consequence to buy the severity down. Stress is a real currency; overflow means trauma.
3. Fight a combat round.
Two dockhands block the gangway. I draw my hook-knife.
start_combat → roll_initiative → attack — initiative order, armor, conditions, and damage all tracked; every attack returns the same five-tier outcome with suggested GM moves on a miss.
4. Watch a clock tick. The patrol you dodged? The GM started a harbor-alert clock. Fail forward enough times (tick_clock fires automatically on partials/failures when wired) and the dock lights come on — consequences arrive on schedule, not by fiat.
That's the loop: fiction in, mechanics out, consequences on clocks.
What's in the box
| Piece | What it gives you |
|---|---|
packages/mcp-server | The MCP server — 134 tools, published as @mythxengine/mcp-server |
packages/engine | Pure, seeded game mechanics (dice, outcomes, combat) |
packages/types / worlds / rulebook | Zod-validated schemas for every entity, plus rules lookup |
packages/storage | SQLite persistence (node:sqlite, zero native deps) |
packages/tools / prompts | Transport-agnostic tool implementations + runtime GM skills |
world-builder/ | The rpg Claude Code plugin (skills, agents, hooks) |
agent-kit/ | Portable GM system prompt + operating manual for any agent |
docs/ | The rulebook + how the engine works |
| 4 bundled worlds | ~13 MB of NPCs, factions, locations, situations, arcs — the demo |
Rules & docs
- [docs/RULEBOOK.md](./docs/RULEBOOK.md) — the complete rules, all 12 chapters (outcomes, position & effect, tests, stress, combat, conditions, gear, time & clocks, GM moves). Generated from
packages/rulebook, the same source thelookup_ruleandgenerate_rulebooktools serve — so it never drifts from the engine. - [docs/engine.md](./docs/engine.md) — how the engine works: the five-tier outcome system, position & effect, stress, deterministic RNG, and how the packages fit together.
- [agent-kit/](./agent-kit/) — a portable GM system prompt and operating manual for running a game with any agent.
Want the full experience?
This repo is the engine. MythxEngine Desktop is the game: a visual frame-based play surface, scene imagery, generated world books, and polish. Follow along and get notified when it ships at mythxengine.com.
Development
pnpm installpnpm build && pnpm test && pnpm lint && pnpm typecheck
See CONTRIBUTING.md — this repo is a downstream mirror of a private monorepo; issues are the fastest way to get fixes in.
License
MIT © protoLabs Studio