diff --git a/packages/meteor-tool/package.js b/packages/meteor-tool/package.js
index 0e03af0536..ce14881702 100644
--- a/packages/meteor-tool/package.js
+++ b/packages/meteor-tool/package.js
@@ -3,15 +3,4 @@ Package.describe({
   version: '1.0.9'
 });
 
-Package.includeTool([
-  'meteor',
-  'livedata',
-  'minifiers',
-  'dev-bundle-fetcher',
-  'js-analyze',
-  'logging',
-  'mongo-livedata',
-  'minimongo',
-  'constraint-solver',
-  'package-version-parser'
-]);
+Package.includeTool();
diff --git a/tools/package-source.js b/tools/package-source.js
index 2b4dc91642..723e33b6ea 100644
--- a/tools/package-source.js
+++ b/tools/package-source.js
@@ -275,12 +275,11 @@ var PackageSource = function (catalog) {
   // to the catalog), so we need to keep track of them.
   self.isTest = false;
 
-  // If this is set, it should be set to an array of package names. We will take
-  // the currently running git checkout and bundle the meteor tool from it
-  // inside this package as a tool. We will include built unipackages for all
-  // the packages in this array as well as their transitive (strong)
-  // dependencies.
-  self.includeTool = null;
+  // If this is set, we will take the currently running git checkout and bundle
+  // the meteor tool from it inside this package as a tool. We will include
+  // built unipackages for all the packages in uniload.ROOT_PACKAGES as well as
+  // their transitive (strong) dependencies.
+  self.includeTool = false;
 
   // If this is true, then this package has no source files. (But the converse
   // is not true: this is only set to true by one particular constructor.) This
@@ -580,19 +579,14 @@ _.extend(PackageSource.prototype, {
         self.pluginInfo[options.name] = options;
       },
 
-      includeTool: function (packages) {
+      includeTool: function () {
         if (!files.inCheckout()) {
           buildmessage.error("Package.includeTool() can only be used with a " +
                              "checkout of meteor");
         } else if (self.includeTool) {
           buildmessage.error("Duplicate includeTool call");
-        } else if (!_.isArray(packages)) {
-          buildmessage.error("Argument to Package.includeTool must be array");
-        } else if (!_.all(packages, _.isString)) {
-          buildmessage.error(
-            "Elements of array passed to Package.includeTool must be strings");
         } else {
-          self.includeTool = packages;
+          self.includeTool = true;
         }
       }
     };
diff --git a/tools/tests/old/test-bundler-assets.js b/tools/tests/old/test-bundler-assets.js
index 70edeebeb2..c4ab8b850f 100644
--- a/tools/tests/old/test-bundler-assets.js
+++ b/tools/tests/old/test-bundler-assets.js
@@ -144,15 +144,6 @@ var runTest = function () {
     });
     assert.strictEqual(fut.wait(), 0);
   });
-
-  console.log("Use Assets API from unipackage");
-  assert.doesNotThrow(function () {
-    var testPackage = uniload.load({
-      library: release.current.library,
-      packages: ['test-package']
-    })['test-package'].TestAsset;
-    testPackage.go(false /* don't exit when done */);
-  });
 };
 
 var Fiber = require('fibers');
diff --git a/tools/uniload.js b/tools/uniload.js
index a9df087f2c..fb597448e8 100644
--- a/tools/uniload.js
+++ b/tools/uniload.js
@@ -6,6 +6,23 @@ var packageLoader = require("./package-loader.js");
 var files = require('./files.js');
 var catalog = require('./catalog.js');
 
+// These are the only packages that may be directly loaded via this package. Add
+// more to the list if you need to uniload more things! (You don't have to
+// include the dependencies of the packages you directly load in this list.)
+var ROOT_PACKAGES = [
+  'constraint-solver',
+  'dev-bundle-fetcher',
+  'ejson',
+  'js-analyze',
+  'livedata',
+  'logging',
+  'meteor',
+  'minifiers',
+  'minimongo',
+  'mongo-livedata',
+  'package-version-parser'
+];
+
 // Load unipackages into the currently running node.js process. Use
 // this to use unipackages (such as the DDP client) from command-line
 // tools (such as 'meteor'). The requested packages will be loaded
@@ -56,6 +73,12 @@ var load = function (options) {
     return cache[cacheKey];
   }
 
+  var undeclaredPackages = _.difference(options.packages, ROOT_PACKAGES);
+  if (undeclaredPackages.length) {
+    throw new Error("attempt to uniload undeclared packages: " +
+                    JSON.stringify(undeclaredPackages));
+  }
+
   // Set up a minimal server-like environment (omitting the parts that
   // are specific to the HTTP server). Kind of a hack. I suspect this
   // will get refactored before too long. Note that
@@ -120,5 +143,6 @@ var load = function (options) {
 
 var uniload = exports;
 _.extend(exports, {
-  load: load
+  load: load,
+  ROOT_PACKAGES: ROOT_PACKAGES
 });
diff --git a/tools/unipackage.js b/tools/unipackage.js
index 215c0e9911..c4f3919b08 100644
--- a/tools/unipackage.js
+++ b/tools/unipackage.js
@@ -11,6 +11,7 @@ var watch = require('./watch.js');
 var packageLoader = require('./package-loader.js');
 var catalog = require('./catalog.js');
 var files = require('./files.js');
+var uniload = require('./uniload.js');
 var Future = require('fibers/future');
 
 var rejectBadPath = function (p) {
@@ -263,7 +264,7 @@ var Unipackage = function () {
   // See description in PackageSource. If this is set, then we include a copy of
   // our own source, in addition to any other tools that were originally in the
   // unipackage.
-  self.includeTool = null;
+  self.includeTool = false;
 
   // This is tools to copy from trees on disk. This is used by the
   // unipackage-merge code in tropohouse.
@@ -970,7 +971,7 @@ _.extend(Unipackage.prototype, {
       catalog: catalog.uniload
     });
     bundler.iterateOverAllUsedUnipackages(
-      localPackageLoader, archinfo.host(), self.includeTool,
+      localPackageLoader, archinfo.host(), uniload.ROOT_PACKAGES,
       function (unipkg) {
         // XXX assert that each name shows up once
         unipkg.saveToPath(path.join(unipath, unipkg.name), {