feat: support for ellmer tools

.Rbuildignore

@@ -6,3 +6,4 @@
 ^pkgdown$
 ^examples$
 ^\.github$
+^\.claude$

.gitignore

@@ -0,0 +1 @@
+.claude/

NAMESPACE

@@ -1,5 +1,6 @@
 # Generated by roxygen2: do not edit by hand
 
+S3method(add_capability,"ellmer::ToolDef")
 S3method(add_capability,prompt)
 S3method(add_capability,resource)
 S3method(add_capability,tool)
@@ -25,6 +26,7 @@ S3method(tools_list,server)
 S3method(write,client_http)
 S3method(write,client_io)
 export(add_capability)
+export(ellmer_to_mcpr_tool)
 export(get_name)
 export(initialize)
 export(new_client_io)

R/ellmer-to-mcpr.R

@@ -0,0 +1,215 @@
+#' Convert ellmer tools to mcpr tools
+#'
+#' This function converts tools from the ellmer package to a format compatible
+#' with the mcpr package. It takes an ellmer ToolDef object and creates an
+#' mcpr tool object with the appropriate input schema and handler function.
+#'
+#' @param ellmer_tool An ellmer ToolDef object created with `ellmer::tool()`
+#' @return An mcpr tool object compatible with `new_tool()`
+#' @export
+#'
+#' @examples
+#' \dontrun{
+#' # Create an ellmer tool
+#' ellmer_rnorm <- ellmer::tool(
+#'   rnorm,
+#'   "Generate random normal numbers",
+#'   n = ellmer::type_integer("Number of observations"),
+#'   mean = ellmer::type_number("Mean value", required = FALSE),
+#'   sd = ellmer::type_number("Standard deviation", required = FALSE)
+#' )
+#'
+#' # Convert to mcpr format
+#' mcpr_tool <- ellmer_to_mcpr_tool(ellmer_rnorm)
+#'
+#' # Add to an mcpr server
+#' server <- new_server("MyServer", "Test server", "1.0.0")
+#' add_capability(server, mcpr_tool)
+#' }
+#'
+#' @seealso [new_tool()], [ellmer::tool()], [add_capability()]
+#' @export
+ellmer_to_mcpr_tool <- function(ellmer_tool) {
+  # Validate input
+  if (!inherits(ellmer_tool, "ellmer::ToolDef")) {
+    stop("ellmer_tool must be a ToolDef object created with ellmer::tool()")
+  }
+
+  # Extract basic information
+  name <- ellmer_tool@name
+  description <- ellmer_tool@description
+  fun <- ellmer_tool@fun
+  convert <- ellmer_tool@convert
+
+  # Convert ellmer type schema to mcpr input schema
+  input_schema <- convert_ellmer_types_to_mcpr(ellmer_tool@arguments)
+
+  # Create handler function that wraps the original ellmer function
+  handler <- function(arguments) {
+    # Convert arguments if needed (similar to ellmer's behavior)
+    if (convert) {
+      # Apply any argument conversion logic here if needed
+      processed_args <- arguments
+    } else {
+      processed_args <- arguments
+    }
+
+    # Call the original function
+    result <- tryCatch(
+      {
+        do.call(fun, processed_args)
+      },
+      error = function(e) {
+        stop("Tool execution error: ", e$message)
+      }
+    )
+
+    response(
+      response_text(
+        yyjsonr::write_json_str(result, list(auto_unbox = TRUE))
+      )
+    )
+  }
+
+  # Create the mcpr tool
+  new_tool(
+    name = name,
+    description = description,
+    input_schema = input_schema,
+    handler = handler
+  )
+}
+
+#' Convert ellmer TypeObject to mcpr schema
+#'
+#' @param type_object An ellmer TypeObject containing the function arguments
+#' @return An mcpr schema object
+#' @keywords internal
+convert_ellmer_types_to_mcpr <- function(type_object) {
+  if (!inherits(type_object, "ellmer::TypeObject")) {
+    stop("Expected TypeObject from ellmer")
+  }
+
+  # Convert each property
+  mcpr_properties <- list()
+  for (prop_name in names(type_object@properties)) {
+    ellmer_type <- type_object@properties[[prop_name]]
+    mcpr_prop <- convert_ellmer_type_to_mcpr_property(ellmer_type, prop_name)
+    mcpr_properties[[prop_name]] <- mcpr_prop
+  }
+
+  # Create the schema
+  schema(
+    properties = do.call(properties, mcpr_properties),
+    additional_properties = type_object@additional_properties
+  )
+}
+
+#' Convert a single ellmer type to an mcpr property
+#'
+#' @param ellmer_type An ellmer Type object (TypeBasic, TypeArray, etc.)
+#' @param prop_name The name of the property (for better error messages)
+#' @return An mcpr property object
+#' @keywords internal
+convert_ellmer_type_to_mcpr_property <- function(ellmer_type, prop_name) {
+  description <- ellmer_type@description %||% prop_name
+  required <- ellmer_type@required
+
+  if (inherits(ellmer_type, "ellmer::TypeBasic")) {
+    type <- ellmer_type@type
+
+    switch(
+      type,
+      "boolean" = property_boolean(
+        title = prop_name,
+        description = description,
+        required = required
+      ),
+      "integer" = property_number(
+        title = prop_name,
+        description = description,
+        required = required,
+        integer = TRUE
+      ),
+      "number" = property_number(
+        title = prop_name,
+        description = description,
+        required = required,
+        integer = FALSE
+      ),
+      "string" = property_string(
+        title = prop_name,
+        description = description,
+        required = required
+      ),
+      # Default to string for unknown basic types
+      property_string(
+        title = prop_name,
+        description = description,
+        required = required
+      )
+    )
+  } else if (inherits(ellmer_type, "ellmer::TypeEnum")) {
+    property_enum(
+      title = prop_name,
+      description = description,
+      values = ellmer_type@values,
+      required = required
+    )
+  } else if (inherits(ellmer_type, "ellmer::TypeArray")) {
+    # Convert the items type
+    items_prop <- convert_ellmer_type_to_mcpr_property(
+      ellmer_type@items,
+      paste0(prop_name, "_item")
+    )
+
+    property_array(
+      title = prop_name,
+      description = description,
+      items = items_prop,
+      required = required
+    )
+  } else if (inherits(ellmer_type, "ellmer::TypeObject")) {
+    # Convert nested object properties
+    nested_properties <- list()
+    for (nested_name in names(ellmer_type@properties)) {
+      nested_type <- ellmer_type@properties[[nested_name]]
+      nested_prop <- convert_ellmer_type_to_mcpr_property(
+        nested_type,
+        nested_name
+      )
+      nested_properties[[nested_name]] <- nested_prop
+    }
+
+    property_object(
+      title = prop_name,
+      description = description,
+      properties = nested_properties,
+      required = required,
+      additional_properties = ellmer_type@additional_properties
+    )
+  } else if (inherits(ellmer_type, "ellmer::TypeJsonSchema")) {
+    # For custom JSON schemas, we'll need to interpret them
+    # This is a complex case that would need custom handling
+    warning(
+      "TypeJsonSchema conversion not fully implemented, converting to string"
+    )
+    property_string(
+      title = prop_name,
+      description = description,
+      required = required
+    )
+  } else {
+    # Unknown type, default to string
+    warning(paste(
+      "Unknown ellmer type:",
+      class(ellmer_type)[1],
+      "- converting to string"
+    ))
+    property_string(
+      title = prop_name,
+      description = description,
+      required = required
+    )
+  }
+}

R/mcp.R

@@ -274,8 +274,17 @@ new_capability <- function(
 #'
 #' @return The MCP object with the capability added
 #' @export
-add_capability <- function(mcp, capability)
+add_capability <- function(mcp, capability) {
   UseMethod("add_capability", capability)
+}
+
+#' @export
+#' @method add_capability ellmer::ToolDef
+`add_capability.ellmer::ToolDef` <- function(mcp, capability) {
+  capability <- ellmer_to_mcpr_tool(capability)
+  mcp$tools[[capability$name]] <- capability
+  invisible(mcp)
+}
 
 #' @export
 #' @method add_capability tool
@@ -284,6 +293,7 @@ add_capability.tool <- function(mcp, capability) {
   invisible(mcp)
 }
 
+
 #' @export
 #' @method add_capability resource
 add_capability.resource <- function(mcp, capability) {

README.md

@@ -154,33 +154,35 @@ print(resource_content)
 
 ## ellmer integration
 
-Use the `register_mcpr_tools` function to convert MCPR tools to ellmer tools and 
-register them with an ellmer chat session.
+Now supports ellmer tools, you can use ellmer's or mcpr's tools,
+interchangeably.
 
-Note that this integration is not standard since ellmer does not currently support
-MCPs. Here we re-recreate the tools obtained via `tools_list` as ellmer tools which
-themselves call `tools_call` to execute the tool.
-The tools are currently not namespaced.
+See the example below, taken from the
+[ellmer documentation](https://ellmer.tidyverse.org/articles/tool-calling.html#defining-a-tool-function)
 
 ```r
-# Create an MCPR client connected to the calculator server
-client <- new_client_io(
-  "Rscript",
-  "path/to/server.R",
-  name = "calculator",
-  version = "1.0.0"
+# create an ellmer tool
+current_time <- ellmer::tool(
+  \(tz = "UTC") {
+    format(Sys.time(), tz = tz, usetz = TRUE)
+  },
+  "Gets the current time in the given time zone.",
+  tz = ellmer::type_string(
+    "The time zone to get the current time in. Defaults to `\"UTC\"`.",
+    required = FALSE
+  )
 )
 
-# Create a Claude chat session with ellmer
-chat <- ellmer::chat_anthropic()
+mcp <- new_server(
+  name = "R Calculator Server",
+  description = "A simple calculator server implemented in R",
+  version = "1.0.0"
+)
 
-## Convert MCPR tools to ellmer tools and register them with the chat
-chat <- register_mcpr_tools(chat, client)
+# register ellmer tool with mcpr server
+mcp <- add_capability(mcp, current_time)
 
-## Try using the tools in a chat
-chat$chat(
-  "Subtract 2 from 44"
-)
+serve_io(mcp)
 ```
 
 ## Using mcpr

_pkgdown.yml

@@ -68,4 +68,5 @@ reference:
     Functions for integrating with the Ellmer package
   contents:
     - register_mcpr_tools
+    - ellmer_to_mcpr_tool
 

docs/pkgdown.yml

@@ -6,7 +6,7 @@ articles:
   client-usage: client-usage.html
   get-started: get-started.html
   practical-examples: practical-examples.html
-last_built: 2025-06-16T08:31Z
+last_built: 2025-06-19T16:39Z
 urls:
   reference: https://mcpr.opifex.org/reference
   article: https://mcpr.opifex.org/articles

examples/ellmer/client.R

@@ -31,5 +31,5 @@ chat <- register_mcpr_tools(chat, client)
 
 ## Try using the tools in a chat
 chat$chat(
-  "Subtract 2 from 44"
+  "What is the current time in the US/Eastern timezone?",
 )