# Using String

> Use the installed String MCP tool for String apps, SFMD, web pages, shell sessions, and commands like /open, /act, /install, or /set.

- Skill: `string-os/using-string-2` (Agent Skill)
- Install (CLI): `npx skillmds@latest add string-os/using-string-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/string-os/using-string-2/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: string-os (https://skillmd.com/u/string-os)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/string-os/using-string-2

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# Using String

You have the installed String MCP tool named `string`; some hosts display it with a server prefix.

Call it with `{ topic, cmd }`, for example `{ "topic": "main", "cmd": "/info" }`.

Use topics like `main`, `app:<name>`, `app:<name>:<config>`, `bash:<name>`, or hubs `app`, `tool`, `bash`, `event`, `system`.

`cmd` must start with `/`; use `/help`, `/info`, and `/act --help` to discover what to do.

Use `/open` to read files, URLs, or apps; installed apps can run `/act.<name>` directly from `app:<name>` if you already know the action.

Use `/edit` to inspect raw files, `/write` to create or overwrite, `/append` to add content, and `/replace` for exact text, block, or line-range edits.

Use `/install` to add apps; `/set $VAR = "..."` for app credentials.

Use topic `event` with `/events`, `/events.read <id>`, and `/events.ack <id>` to handle local webhook messages.

Claude Code may also receive those webhook messages through the String channel, but ack still happens with `/events.ack <id>`.

Read the payload inside `<𝒞=string:TOPIC>...</𝒞>` and follow `Recovery:` or `next:` hints.