Arcotheon is a registry and a package format for agent capabilities: skills, tools, workflows, knowledge and the assets that go with them. This page takes you from nothing to a running tool.
Requirements#
- Node.js 22.12 or newer.
- For running tools: Linux with bubblewrap (
bwrap) and unprivileged user namespaces. Installing and verifying work everywhere; see the security page for what runs where. - Python 3.9 or newer for capabilities that ship Python tools.
Install the CLI#
Arcotheon 0.1 is distributed from its repository. It is not published to npm yet.
git clone https://github.com/sarja-technologies/arcotheon
cd arcotheon
npm ci && npm run build
node packages/cli/dist/main.js helpAlias it as arcotheon for the rest of this page.
Point it at the registry#
The directory at agdc.dev/arcotheon serves a signed registry, and it is the CLI's default (--registry, or the ARCOTHEON_REGISTRY environment variable, change it). The CLI trusts the registry root key built into the SDK.
The registry currently lists one capability, the Example .adcap: a skill, two tools and documentation, small enough to read in full. It asks for no permissions. Everything below was run against it, and the output is what the CLI printed.
arcotheon searchsarja/example-adcap 1.0.0 free A small, complete example of an .adcap capability: a skill, two tools and documentation. Install it to see how packages work.arcotheon info sarja/example-adcapsarja/example-adcap
1.0.0 2026-10-24 free/public
A small, complete example of an .adcap capability: a skill, two tools and documentation. Install it to see how packages work.
permissions: none deps: noneInstall a capability#
arcotheon install sarja/example-adcap✓ installed sarja/[email protected]The CLI resolves versions and dependencies, downloads the archive, checks its hash and signature, and shows you the permissions the capability asks for before anything is written. Installing never runs the capability's code. The Example asks for no permissions, so there was nothing to approve. A capability that does ask lists each permission with the reason its publisher gave, and waits for your answer. Use --yes to approve non-interactively; without it, a capability that asks for permissions is refused.
To see what a package contains before or after installing it:
arcotheon inspect sarja/example-adcapsarja/[email protected] — Example .adcap
A small, complete example of an .adcap capability: a skill, two tools and documentation. Install it to see how packages work.
Skills 1 · Tools 2 · Workflows 0 · Knowledge 0 · Assets 0 · Remote resources 0
Executable tools (never run until you call them):
shout [node] Return the text in upper case. The smallest possible tool: no files, no network, no permissions.
word_count [node] Count the words, characters and lines in some text. Shows a tool that returns structured results.
Permissions requested: noneRun a tool#
arcotheon run sarja/example-adcap shout --input '{"text":"hello arcotheon"}' --workspace .{
"text": "HELLO ARCOTHEON"
}arcotheon run sarja/example-adcap word_count --input '{"text":"one two three\nfour"}' --workspace .{
"words": 4,
"characters": 18,
"lines": 2
}The tool runs in a sandbox that can see only what its permissions allow. The Example's tools declare none.
--workspace must be a project directory that neither contains nor sits inside the Arcotheon store (~/.arcotheon by default). Run these from a project folder; from your home directory the CLI refuses with PERMISSION_DENIED and says the workspace overlaps the store.
Use it from an agent#
Arcotheon speaks the Model Context Protocol, so any MCP-capable agent can call installed tools:
arcotheon mcp --workspace "$PWD"Point your agent's MCP configuration at that command. Only tools whose permissions you approved are listed. Skills are plain Agent Skills directories; arcotheon skills prints where each one lives so you can link it into an agent that reads skills from a folder.
Keep things current#
arcotheon list # what is installed, and older versions kept for rollbacksarja/example-adcap 1.0.0 directarcotheon update # newer versions within the same major; asks again if permissions grewEverything is up to date.arcotheon doctor # integrity, compatibility, revoked or deprecated versions✓ sarja/example-adcaparcotheon cache prefetch sarja/example-adcap # make a later install work offlineCached sarja/[email protected] for offline install.arcotheon rollback <id> [version] returns to a version the CLI kept; there is only one version of the Example, so there is nothing to roll back to yet.