mcp_client() connects to an MCP server over Streamable HTTP, so a Shiny
app can host the server's apps with mcp_host_server() and
mcp_chat_host(). Any server works: an app deployed with
mcp_endpoint(), a Shiny app served by Shiny's own MCP support, or a
server written in another language.
The client speaks both generations of the protocol: the stateless
2026-07-28 revision, and the initialize handshake of 2025-11-25 and
earlier. It tells the server it can show MCP Apps, and it keeps the
_meta of every result, which is where an app's page is declared.
Nothing is sent until the client is first used.
Arguments
- url
The server's MCP endpoint, such as
"https://connect.example.com/sales/mcp".- headers
Headers to send with every request, such as
Authorization: a named list, or a function that returns one.- name
A name for the server, unique among the sources a Shiny app hosts. Saved conversations refer to the server's apps by this name, so keep it stable. Defaults to the URL's host and path.
- timeout
Seconds to wait for each response. Apps that poll their server, as Shiny apps can, need this to be longer than their polls.
Value
An McpClient.
Credentials
headers can be a function, called before each request. To send each
visitor's own credentials, create the client in the Shiny server
function, where the function can read the visitor's session. A client
created outside it is shared by every session, along with its
connection and the tool list it has read.
Headers go wherever url points, so use https:// for anything
secret.
See also
Other hosting:
as_shinychat_tool(),
mcp_chat_host(),
mcp_host_ui()
Examples
if (FALSE) { # \dontrun{
client <- mcp_client(
"https://connect.example.com/sales/mcp",
headers = list(Authorization = paste("Key", Sys.getenv("CONNECT_API_KEY")))
)
client$tools()
client$call_tool("open_sales_app", list(region = "West"))
} # }