feat: implement Agent Skills

DESCRIPTION

@@ -99,6 +99,7 @@ Collate:
     'mcp.R'
     'task_create_btw_md.R'
     'task_create_readme.R'
+    'task_create_skill.R'
     'tool-result.R'
     'tool-agent-subagent.R'
     'tool-agent-custom.R'
@@ -121,6 +122,7 @@ Collate:
     'tool-run.R'
     'tool-session-package-installed.R'
     'tool-sessioninfo.R'
+    'tool-skills.R'
     'tool-web.R'
     'tools.R'
     'utils-ellmer.R'

NAMESPACE

@@ -26,9 +26,12 @@ export(btw_app)
 export(btw_client)
 export(btw_mcp_server)
 export(btw_mcp_session)
+export(btw_skill_install_github)
+export(btw_skill_install_package)
 export(btw_task)
 export(btw_task_create_btw_md)
 export(btw_task_create_readme)
+export(btw_task_create_skill)
 export(btw_this)
 export(btw_tool_agent_subagent)
 export(btw_tool_cran_package)
@@ -73,6 +76,7 @@ export(btw_tool_session_platform_info)
 export(btw_tool_sessioninfo_is_package_installed)
 export(btw_tool_sessioninfo_package)
 export(btw_tool_sessioninfo_platform)
+export(btw_tool_skill)
 export(btw_tool_web_read_url)
 export(btw_tools)
 export(edit_btw_md)

R/btw_client.R

@@ -151,12 +151,16 @@ btw_client <- function(
   llms_txt <- read_llms_txt(path_llms_txt)
   project_context <- c(llms_txt, config$btw_system_prompt)
   project_context <- paste(project_context, collapse = "\n\n")
+  skills_prompt <- btw_skills_system_prompt()
 
   sys_prompt <- c(
     btw_prompt("btw-system_session.md"),
     if (!skip_tools) {
       btw_prompt("btw-system_tools.md")
     },
+    if (nzchar(skills_prompt)) {
+      skills_prompt
+    },
     if (nzchar(project_context)) {
       btw_prompt("btw-system_project.md")
     },
@@ -170,6 +174,8 @@ btw_client <- function(
     client$set_tools(tools = c(client$get_tools(), config$tools))
   }
 
+  warn_skills_without_read_file(client$get_tools())
+
   client
 }
 
@@ -661,3 +667,16 @@ remove_hidden_content <- function(text) {
 
   paste(lines[starts - shift(cumsum(ends)) <= 0], collapse = "\n")
 }
+
+warn_skills_without_read_file <- function(tools) {
+  tool_names <- names(tools)
+  has_skills <- "btw_tool_skill" %in% tool_names
+  has_read_file <- "btw_tool_files_read" %in% tool_names
+  if (has_skills && !has_read_file) {
+    cli::cli_warn(c(
+      "The {.fn btw_tool_skill} tool is enabled but {.fn btw_tool_files_read} is not.",
+      "i" = "Skills work best with the read file tool, which lets the model read skill resource files.",
+      "i" = "Add {.code btw_tools(\"files\")} or enable {.fn btw_tool_files_read} to get full skill support."
+    ))
+  }
+}

R/btw_client_app.R

@@ -270,6 +270,43 @@ btw_app_from_client <- function(
       }
     })
 
+    skills_read_file_mismatch <- shiny::reactive({
+      sel <- selected_tools()
+      "btw_tool_skill" %in% sel && !"btw_tool_files_read" %in% sel
+    })
+
+    shiny::observeEvent(skills_read_file_mismatch(), {
+      if (isTRUE(skills_read_file_mismatch())) {
+        notifier(
+          id = "skills_read_file_mismatch",
+          shiny::icon("triangle-exclamation", class = "text-warning"),
+          shiny::tagList(
+            shiny::HTML(
+              "The <strong>Load Skill tool</strong> works best with the <strong>Read File tool</strong> enabled"
+            ),
+            shiny::actionButton(
+              class = "btn-sm mt-2",
+              "enable_read_file_tool",
+              "Enable Read File Tool"
+            )
+          )
+        )
+      }
+    })
+
+    shiny::observeEvent(input$enable_read_file_tool, {
+      file_tools <- c(input$tools_files, "btw_tool_files_read")
+      shiny::updateCheckboxGroupInput(
+        session = session,
+        inputId = "tools_files",
+        selected = file_tools
+      )
+      bslib_hide_toast <- asNamespace("bslib")[["hide_toast"]]
+      if (!is.null(bslib_hide_toast)) {
+        bslib_hide_toast("skills_read_file_mismatch")
+      }
+    })
+
     output$ui_other_tools <- shiny::renderUI({
       if (length(other_tools) == 0) {
         return(NULL)
@@ -392,6 +429,47 @@ btw_app_from_client <- function(
 
 # Status Bar ----
 
+notifier <- function(icon, action, error = NULL, ...) {
+  error_body <- if (!is.null(error)) {
+    shiny::p(shiny::HTML(sprintf("<code>%s</code>", error$message)))
+  }
+
+  bslib_toast <- asNamespace("bslib")[["toast"]]
+  bslib_show_toast <- asNamespace("bslib")[["show_toast"]]
+  bslib_toast_header <- asNamespace("bslib")[["toast_header"]]
+
+  if (is.null(bslib_toast) || is.null(bslib_show_toast)) {
+    if (!is.null(error)) {
+      body <- shiny::span(icon, action)
+    } else {
+      body <- shiny::tagList(
+        shiny::p(
+          shiny::icon("warning"),
+          "Failed to update system prompt",
+          class = "fw-bold"
+        ),
+        error_body
+      )
+    }
+    shiny::showNotification(
+      body,
+      type = if (is.null(error)) "message" else "error"
+    )
+    return()
+  }
+
+  toast <- bslib_toast(
+    if (is.null(error)) action else error_body,
+    header = if (!is.null(error)) {
+      bslib_toast_header(action, icon = icon)
+    },
+    icon = if (is.null(error)) icon,
+    position = "top-right",
+    ...
+  )
+  bslib_show_toast(toast)
+}
+
 btw_status_bar_ui <- function(id, provider_model) {
   ns <- shiny::NS(id)
   shiny::tagList(
@@ -575,46 +653,6 @@ btw_status_bar_server <- function(id, chat) {
         shiny::showModal(modal)
       })
 
-      notifier <- function(icon, action, error = NULL) {
-        error_body <- if (!is.null(error)) {
-          shiny::p(shiny::HTML(sprintf("<code>%s</code>", error$message)))
-        }
-
-        bslib_toast <- asNamespace("bslib")[["toast"]]
-        bslib_show_toast <- asNamespace("bslib")[["show_toast"]]
-        bslib_toast_header <- asNamespace("bslib")[["toast_header"]]
-
-        if (is.null(bslib_toast) || is.null(bslib_show_toast)) {
-          if (!is.null(error)) {
-            body <- shiny::span(icon, action)
-          } else {
-            body <- shiny::tagList(
-              shiny::p(
-                shiny::icon("warning"),
-                "Failed to update system prompt",
-                class = "fw-bold"
-              ),
-              error_body
-            )
-          }
-          shiny::showNotification(
-            body,
-            type = if (is.null(error)) "message" else "error"
-          )
-          return()
-        }
-
-        toast <- bslib_toast(
-          if (is.null(error)) action else error_body,
-          header = if (!is.null(error)) {
-            bslib_toast_header(action, icon = icon)
-          },
-          icon = if (is.null(error)) icon,
-          position = "top-right"
-        )
-        bslib_show_toast(toast)
-      }
-
       shiny::observeEvent(
         input$system_prompt,
         ignoreInit = TRUE,
@@ -691,7 +729,7 @@ app_tool_group_inputs <- function(tools_df, initial_tool_names = NULL) {
 
   # then other, then deprecated (if shown)
   group_names <- names(tools_df)
-  priority_groups <- c("agent", "docs", "files", "env")
+  priority_groups <- c("agent", "skills", "docs", "files", "env")
   trailing_groups <- c("other", "deprecated")
   priority_present <- intersect(priority_groups, group_names)
   middle_groups <- sort(setdiff(
@@ -737,6 +775,7 @@ app_tool_group_choice_input <- function(
     "pkg" = shiny::span(label_icon, "Package Tools"),
     "run" = shiny::span(label_icon, "Run Code"),
     "sessioninfo" = shiny::span(label_icon, "Session Info"),
+    "skills" = shiny::span(label_icon, "Skills"),
     "web" = shiny::span(label_icon, "Web Tools"),
     "other" = shiny::span(label_icon, "Other Tools"),
     to_title_case(group)

R/mcp.R

@@ -153,7 +153,7 @@
 #'
 #' @name mcp
 #' @export
-btw_mcp_server <- function(tools = btw_tools()) {
+btw_mcp_server <- function(tools = btw_mcp_tools()) {
   # If given a path to an R script, we'll pass it on to mcp_server()
   is_likely_r_file <-
     is.character(tools) &&
@@ -172,3 +172,16 @@ btw_mcp_server <- function(tools = btw_tools()) {
 btw_mcp_session <- function() {
   mcptools::mcp_session()
 }
+
+btw_mcp_tools <- function() {
+  # Skills are excluded from MCP by default: the skill system prompt
+  # (with <available_skills> metadata) is injected by btw_client(), not by
+  # MCP. Without that context the model has no way to know which skills are
+  # available. Filesystem-based agents (e.g. Claude Code) can read SKILL.md
+  # files directly via their <location> paths in the system prompt.
+  all_tools <- btw_tools()
+  Filter(
+    function(tool) !identical(tool@annotations$btw_group, "skills"),
+    all_tools
+  )
+}