Skip to contents

Serve MCP Apps to an MCP client

Source: R/serve.R
serve.Rd

serve() starts an MCP server for an app and blocks until the client disconnects (stdio) or you interrupt it (HTTP).

  • type = "stdio", the default, is for desktop clients such as Claude Desktop, VS Code, and Goose, which start the R process themselves and talk to it over standard input and output. Put serve(app) at the end of a script and register Rscript /path/to/script.R with the client.

  • type = "http" runs a long-lived Streamable HTTP server at http://host:port/mcp, for clients that connect to a URL. To deploy to Posit Connect, use mcp_endpoint() instead.

The server speaks MCP protocol versions 2024-11-05 through 2025-11-25 (with an initialize handshake) and 2026-07-28 (stateless, no handshake), and the MCP Apps extension (2026-01-26). Clients that don't support MCP Apps still get every tool the model may call, and see text results instead of the app; tools only an app may call are left out.

Usage

serve(
  app,
  type = c("stdio", "http"),
  port = 8080,
  host = "127.0.0.1",
  path = "/mcp",
  allowed_origins = NULL,
  allowed_hosts = NULL,
  ...
)

Arguments

app

An McpApp, a list of apps to serve from one server, a Shiny app object, or a path to a directory containing an app.R (or ui.R and server.R). Shiny apps run live; see as_mcp_app().

type

"stdio" or "http".

port, host

Where the HTTP server listens. The default host only accepts connections from this machine; use "0.0.0.0" to listen on all interfaces, and put the server behind authentication.

path

The HTTP endpoint path.

allowed_origins

Browser origins, besides the server's own and loopback ones for a local server, allowed to call the HTTP endpoint, for example "https://chat.example.com". Use "*" to allow any.

allowed_hosts

For a server listening on this machine only, the host names it may be reached at besides localhost and IP addresses, such as the public name of a reverse proxy in front of it. Requests for any other host are refused, which protects a local server from web pages that point their own host name at it (DNS rebinding).

...

Unused; for future extensions.

Value

Nothing; serve() runs until the connection closes.

See also

Other serving: mcp_endpoint(), preview_app(), shinymcp-options

Examples

if (FALSE) { # \dontrun{
# app.R, registered with Claude Desktop as `Rscript /path/to/app.R`
library(shinymcp)
app <- mcp_app(ui, tools, name = "explorer")
serve(app)

# An existing Shiny app, served live
serve("path/to/shiny-app")

# Over HTTP
serve(app, type = "http", port = 8080)
} # }