String MCP
A browser for agents: one command set reads websites, Markdown, files and apps and calls their actions.
- 78 ★ on the repository
- Last commit
- MIT
Extended access
Why this level
- The daemon listens on a local port and accepts webhooks
- Local apps can run shell commands on your machine
Install
- Works in
Manual install
/plugin marketplace add string-os/stringThe first of two plugin commands in Claude Code.
Access and checks
How we reviewExtended accessThe tool runs code or makes network calls and only reads external data.
- The daemon listens on a local port and accepts webhooks
- Local apps can run shell commands on your machine
This is third-party code. Review the repository files before installing.
What it does
String unifies apps, web pages and Markdown documents into one surface for an agent. The `/open` command reads a document, page, file or shell session, `/act` calls an available action and `/info` shows where the agent is. A site can describe navigation and actions in SFMD (Markdown with action blocks), while ordinary pages open as clean Markdown. Responses carry `next:` hints and action schemas are visible through `/act --help`. String runs as a CLI, a daemon or a single MCP tool named `string`, installed as a Claude Code plugin or through npm.
Who it is for. Agent developers and site owners who want to give an agent one way to read pages and call actions without a separate schema per tool.
Good fit when
- An agent must read site documentation as clean Markdown.
- An installed app must expose actions to an agent: feed, read, comment, search.
- Local webhooks must reach an agent as events in an inbox.
- A site must serve both people and agents: pages gain a mirrored `.md`.
Not a fit when
- Ordinary search and page reading are enough: a separate agent browser is overkill.
- A familiar MCP server for a specific service with a ready toolset is needed.
- An environment without Node.js: running needs Node and npm.
Example request
Open docs.string-os.org as Markdown, find the MCP section and list the available actions.MCP
- Transport
- stdio
- Authentication
- not required
Limitations
Running needs Node.js and the daemon starts itself on port `3923`. Web pages can call web APIs, while local shell commands run only from local files and installed apps: the boundary is built into the project, yet any installed String app gets access to your machine, so install apps only from trusted sources. Secrets are set inside an app with `/set $VAR`, not in the prompt. The SFMD format is specific to String and few third-party sites use it.
How to disable. Remove the `string` plugin through `/plugin` or the package with `npm uninstall -g @string-os/string`, then stop the daemon. Delete the String data directory separately.
FAQ
Which command installs it in Claude Code?
Two commands in a session: `/plugin marketplace add string-os/string` and `/plugin install string@string-os`. The plugin adds the MCP tool and a short skill.
How do I connect String as MCP by hand?
Add the `string` server with the command `npx` and arguments `-y @string-os/string --mcp`. No separate package is needed.
What is SFMD?
String Flavored Markdown: ordinary Markdown with navigation, action blocks and response conventions.
How do I set a secret for an app?
Inside the app topic with `/set $VAR = "..."`. The value does not enter the agent prompt.
Where do I find ready apps?
The `string-os/apps` repository collects available String apps.
Discussion
No questions or reviews yet.
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README in short
The README explains the `/open`, `/act`, `/info` model, the SFMD format, running as CLI, daemon and MCP, webhooks and safety. It lists packages and links a plugin for building sites.