Published components

Twenty-two components are published to actpkg.dev/library, signed in CI with keyless cosign. The registry is the source of truth for versions and digests; this page is about which one you want.

Any of them runs the same way:

act info actpkg.dev/library/<name> --tools     # what it does, and what it will ask for
act run  actpkg.dev/library/<name> --mcp       # serve it to an agent

Before you pick one

Two questions decide how much wiring a component needs, and act info answers both without running anything:

• Does it declare capabilities? A pure component (crypto, encoding, random, time) declares none and needs no grant at all. Anything touching files, the network, or sockets declares a ceiling you must grant within — see Policy & sandbox.
• Does it need a session? Anything holding a connection or a credential does. If a call fails with std:session-not-found, that is what happened — see Sessions.

By what it is for

Data and storage — sqlite, postgres, filesystem, archive

Query a database or work with files under a path you choose. These are the components where the grant matters most: scope it to the directory the data lives in, not to /.

Network — http-client, search-brave, search-searxng

Fetch a URL, or search the web. The declared wasi:http ceiling limits which hosts a component can reach at all, so a search component cannot quietly become a general-purpose fetcher.

Documents — anydoc, pdf-inspector

Extract text and structure out of formats an agent cannot read directly.

Compute — python-env, python-eval, sed

Run code in a sandbox. python-env is the substantial one: a stateful Python environment with numpy and pandas built in and runtime pip install. python-eval is the narrow, pure-Python sandbox. Try python-env in a browser tab on the playground.

Browser and desktop — webdriver-bidi, vnc-desktop

Drive a real browser or a remote desktop from an agent.

Bridges — mcp-bridge, openapi-bridge

Adapt something that already exists into a component: an upstream MCP server, or an OpenAPI service. These are stateful — the parsed spec or the upstream handshake lives in a session.

act-http-bridge is also published but deprecated: it fronted the REST binding, which no longer exists. It stays buildable so nothing breaks; do not start anything new on it.

Utilities — crypto, encoding, random, time, openwallet

Small, mostly pure. Useful on their own and useful as worked examples: they are the simplest components to read if you are about to write one.

Writing your own

Everything above is built with the same toolchain you would use:

act-build init rust my-component

See the Rust or Python quick start — or Language support if you would rather use one of the other ten.