Create an R-based MCP server entry for mcp_servers

Builds a mcp_servers list entry that launches an R subprocess running mcptools::mcp_server() over stdio. Requires the mcptools and ellmer packages to be installed on the system.

Usage

r_mcp_server(
  tools_script = NULL,
  session_tools = FALSE,
  rscript = file.path(R.home("bin"), if (.Platform$OS.type == "windows") "Rscript.exe"
    else "Rscript")
)

Arguments

tools_script

Character(1) or NULL. Path to an .R script that, when sourced, yields a list() of ellmer::tool() objects. When NULL only the built-in session tools are exposed (controlled by session_tools).

session_tools

Logical. Whether to expose the built-in mcptools session-management tools (list_r_sessions, select_r_session). Default FALSE for embedding use-cases.

rscript

Character(1). Absolute path to the Rscript binary. Defaults to the binary of the currently running R installation (Rscript on Linux/macOS, Rscript.exe on Windows), resolved via R.home("bin") — always an absolute path, independent of PATH. Falls back to Sys.which("Rscript") if that path does not exist. Pass an explicit path to use a specific R installation.

Value

A named list with type, command, and args suitable for use as a value inside ClaudeAgentOptions(mcp_servers = list(...)).

Details

Defining tools

Create a standalone .R script that returns a list() of ellmer::tool() objects (this is the value mcptools::mcp_server() accepts via its tools argument):

# my_tools.R
library(ellmer)
list(
  ellmer::tool(
    fun         = function(a, b) a + b,
    description = "Add two numbers",
    arguments   = list(
      a = ellmer::type_number("First number"),
      b = ellmer::type_number("Second number")
    )
  )
)

Then pass the script path:

options <- ClaudeAgentOptions(
  mcp_servers   = list(my_tools = r_mcp_server("my_tools.R")),
  allowed_tools = "mcp__my_tools__add"
)

Examples

# Create an MCP server entry from a tools script
entry <- r_mcp_server("my_tools.R")
entry$type    # "stdio"
#> [1] "stdio"
entry$command # path to Rscript
#> [1] "/opt/R/4.6.0/lib/R/bin/Rscript"

# Use in ClaudeAgentOptions
if (FALSE) { # \dontrun{
opts <- ClaudeAgentOptions(
  mcp_servers   = list(my_tools = r_mcp_server("my_tools.R")),
  allowed_tools = "mcp__my_tools__add"
)
} # }