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on-croft/croft

v1.1.0MIT

Build, deploy, and maintain apps on a Croft workspace through the Croft MCP, plus skills that teach agents the Croft golden path, connectors, and shared data.

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Croft Agent Plugin

Agent Plugin 1.0.0 Version License: MIT

One step to make any compatible AI agent a Croft builder — the tools and the know-how.

A portable Agent Plugin 1.0.0 for Croft — a passwordless PaaS where you build, deploy, and maintain small web apps by talking to an AI assistant.

It installs natively in Cursor and Claude Code, and in any other Agent Plugin 1.0.0-compatible client. Point a client at this plugin and your agent gets two things:

  1. The Croft MCP server (mcp.json) — the tools to create apps, write files, deploy, manage connectors and shared data, and more, on the user's Croft workspace.
  2. Skills (skills/) — portable instructions that teach the agent Croft's golden path, so it builds apps the right way from the very first turn, even before it reads the live conventions.

Most MCP setups hand an agent some tools and hope it figures out the rest. This plugin gives it the tools and the conventions — so it behaves like a Croft expert from message one.

What your agent can do once installed

  • Build and ship apps — the full create_app → write_files → deploy → poll status path, following Croft's conventions (Node/Hono/SQLite, $PORT, /healthz, no auth code, secrets, file uploads, public paths, scheduled tasks).
  • Reach outside tools — call external APIs (Stripe, a CRM, email, Azure DevOps, …) through connectors, never a vendor SDK or a key stored in code.
  • Share data between apps in the workspace (e.g. one shared contacts list).

Install

There are no credentials to configure in any client (see Authentication).

Cursor (recommended) — add this repository as a plugin marketplace, then install the croft plugin. This is the route that installs the MCP server and the skills:

Cursor Settings → Plugins → Add marketplace → https://github.com/on-croft/agent-plugin

You can also point Cursor at a local clone of the folder — it reads .cursor-plugin/marketplace.json.

Cursor, one click, MCP server only — this install link adds the Croft MCP server to Cursor without the marketplace step:

Install MCP Server

It installs the tools, not the know-how. Cursor's deeplinks only cover MCP servers — there is no plugin-install deeplink — so this route skips skills/ entirely. Your agent gets Croft's tools but not its conventions, which is exactly the gap this plugin exists to close. Prefer the marketplace install above; use the link when you only want the server.

How the link is built

cursor://anysphere.cursor-deeplink/mcp/install?name=<name>&config=<base64>, where the config is the base64 of a single server entry:

{"type":"http","url":"https://mcp.oncroft.net"}

printf '{"type":"http","url":"https://mcp.oncroft.net"}' | base64
# eyJ0eXBlIjoiaHR0cCIsInVybCI6Imh0dHBzOi8vbWNwLm9uY3JvZnQubmV0In0=

Regenerate it if the endpoint ever changes.

Claude Code — add the marketplace and install:

claude plugin marketplace add on-croft/agent-plugin
claude plugin install croft@croft

Any other Agent Plugin 1.0.0 client — point it at this repository, or drop the directory into the client's plugin location. It discovers the root plugin.json, mcp.json, and skills/ automatically.

https://github.com/on-croft/agent-plugin

What's inside

agent-plugin/
├── plugin.json                     # Agent Plugin 1.0.0 manifest
├── mcp.json                        # Croft MCP server (remote, streamable-http)
├── .cursor-plugin/
│   ├── marketplace.json            # Cursor marketplace manifest (this repo = one plugin)
│   ├── plugin.json                 # Cursor plugin manifest
│   └── mcp.json                    # same server, Cursor's `type: http` spelling
├── .claude-plugin/
│   ├── marketplace.json            # Claude Code marketplace manifest
│   └── plugin.json                 # Claude Code plugin manifest (points at ../mcp.json)
├── assets/
│   ├── logo.svg                    # Croft brand icon — shown by Cursor's marketplace
│   └── logo.png                    # 1024px raster of the same icon
└── skills/
    ├── building-croft-apps/        # the create → write → deploy → verify golden path
    ├── croft-connectors/           # calling external APIs via connectors (no SDKs, no keys)
    └── croft-shared-data/          # sharing SQLite data between apps

The same skills/ directory and the same MCP endpoint serve every client — the client-specific directories only carry each host's manifest format. Keep the version field in sync across the four manifests when releasing.

assets/logo.svg is Croft's brand icon, copied from the marketing site. Only Cursor renders it (via logo in both of its manifests) — the Agent Plugin 1.0.0 spec and Claude Code have no logo field. It's the light tile, which carries its own background so it reads on light and dark marketplace themes alike.

The MCP server

mcp.json declares Croft's remote MCP endpoint:

{
  "mcpServers": {
    "croft": { "type": "streamable-http", "url": "https://mcp.oncroft.net" }
  }
}

Cursor spells the same transport "type": "http", so .cursor-plugin/mcp.json carries an identical server under that name. Both point at https://mcp.oncroft.net.

Authentication

Per-user OAuth — never a static key, which is why no credentials appear in mcp.json (the spec forbids credentials in package data anyway). On first connect the agent's client performs OAuth 2.1 (PKCE + dynamic client registration) against https://mcp.oncroft.net; the user signs in and authorises their workspace, and every request is then scoped to that workspace with the user's role. Only workspace builders (owner/admin/creator) can use the build tools.

In agents that authenticate the MCP server per end-user (e.g. Microsoft Copilot's User auth mode), each user connects with their own Croft identity and role — which is the intended setup. Avoid shared/maker-credential modes.

The skills

SkillUse it when
building-croft-appsCreating, changing, deploying, or fixing any Croft app — the required create_app → write_files → deploy → poll status workflow and Croft's app conventions.
croft-connectorsThe app must call an external API (Stripe, Azure DevOps, a CRM, email…) — always through a connector, never a vendor SDK or a stored key.
croft-shared-dataTwo apps in the workspace should reuse the same data (e.g. a shared contacts list), or one app needs to read another's data.

The skills summarise Croft's get_platform_conventions, which the agent should still call at runtime — it returns the authoritative, live golden path plus the workspace's actual connectors and shared apps.

Learn more

License

MIT — see LICENSE.