diff --git a/repl.lua b/repl.lua
index 70ad6f3..eaac1e1 100644
--- a/repl.lua
+++ b/repl.lua
@@ -483,9 +483,13 @@ function M.run(config)
                     renderer.status("usage: :mcp tool <alias.name>"); return
                 end
                 local alias, tname = name:match("^([^.]+)%.(.+)$")
-                local sess = alias and mcp_sessions[alias]
+                if not alias then
+                    renderer.status("tool name missing alias prefix: " .. name)
+                    return
+                end
+                local sess = mcp_sessions[alias]
                 if not sess then
-                    renderer.status("unknown alias: " .. tostring(alias))
+                    renderer.status("unknown alias: " .. alias)
                     return
                 end
                 local found