diff --git a/tools/toolchains/__init__.py b/tools/toolchains/__init__.py
index 6dd9d31c3c8..512c3476e44 100644
--- a/tools/toolchains/__init__.py
+++ b/tools/toolchains/__init__.py
@@ -188,6 +188,23 @@ def __str__(self):
 }
 
 
+def check_toolchain_path(function):
+    """Check if the path to toolchain is valid. Exit if not.
+    Use this function as a decorator.  Causes a system exit if the path does
+    not exist. Execute the function as normal if the path does exist.
+
+    Positional arguments:
+    function -- the function to decorate
+    """
+    def perform_check(self, *args, **kwargs):
+        if not exists(self.toolchain_path):
+            error_string = 'Could not find executable for %s.\n Currently ' \
+                           'set search path: %s'% (self.name, self.toolchain_path)
+            raise Exception(error_string)
+        return function(self, *args, **kwargs)
+    return perform_check
+
+
 class mbedToolchain:
     # Verbose logging
     VERBOSE = True
@@ -702,6 +719,7 @@ def get_arch_file(self, objects):
 
     # THIS METHOD IS BEING CALLED BY THE MBED ONLINE BUILD SYSTEM
     # ANY CHANGE OF PARAMETERS OR RETURN VALUES WILL BREAK COMPATIBILITY
+    @check_toolchain_path
     def compile_sources(self, resources, build_path, inc_dirs=None):
         # Web IDE progress bar for project build
         files_to_compile = resources.s_sources + resources.c_sources + resources.cpp_sources
@@ -900,6 +918,7 @@ def compile_output(self, output=[]):
             else:
                 raise ToolException(_stderr)
 
+    @check_toolchain_path
     def build_library(self, objects, dir, name):
         needed_update = False
         lib = self.STD_LIB_NAME % name
@@ -911,6 +930,7 @@ def build_library(self, objects, dir, name):
 
         return needed_update
 
+    @check_toolchain_path
     def link_program(self, r, tmp_path, name):
         needed_update = False
         ext = 'bin'
diff --git a/tools/toolchains/arm.py b/tools/toolchains/arm.py
index cb55f731446..a7ecc848a49 100644
--- a/tools/toolchains/arm.py
+++ b/tools/toolchains/arm.py
@@ -15,12 +15,12 @@
 limitations under the License.
 """
 import re
-from os.path import join, dirname, splitext, basename, exists
+from os.path import join, dirname, splitext, basename
+from distutils.spawn import find_executable
 
 from tools.toolchains import mbedToolchain, TOOLCHAIN_PATHS
 from tools.hooks import hook_tool
 from tools.utils import mkdir
-import copy
 
 class ARM(mbedToolchain):
     LINKER_EXT = '.sct'
@@ -56,6 +56,11 @@ def __init__(self, target, options=None, notify=None, macros=None, silent=False,
         else:
             cpu = target.core
 
+        if not TOOLCHAIN_PATHS['ARM']:
+            exe = find_executable('armcc')
+            if exe:
+                TOOLCHAIN_PATHS['ARM'] = dirname(dirname(exe))
+
         ARM_BIN = join(TOOLCHAIN_PATHS['ARM'], "bin")
         ARM_INC = join(TOOLCHAIN_PATHS['ARM'], "include")
         
@@ -81,6 +86,8 @@ def __init__(self, target, options=None, notify=None, macros=None, silent=False,
         self.ar = join(ARM_BIN, "armar")
         self.elf2bin = join(ARM_BIN, "fromelf")
 
+        self.toolchain_path = TOOLCHAIN_PATHS['ARM']
+
     def parse_dependencies(self, dep_path):
         dependencies = []
         for line in open(dep_path).readlines():
diff --git a/tools/toolchains/gcc.py b/tools/toolchains/gcc.py
index b9c79a8abea..add6b7e0b93 100644
--- a/tools/toolchains/gcc.py
+++ b/tools/toolchains/gcc.py
@@ -16,6 +16,7 @@
 """
 import re
 from os.path import join, basename, splitext, dirname, exists
+from distutils.spawn import find_executable
 
 from tools.toolchains import mbedToolchain, TOOLCHAIN_PATHS
 from tools.hooks import hook_tool
@@ -110,6 +111,11 @@ def __init__(self, target, options=None, notify=None, macros=None, silent=False,
         self.ar = join(tool_path, "arm-none-eabi-ar")
         self.elf2bin = join(tool_path, "arm-none-eabi-objcopy")
 
+        if tool_path:
+            self.toolchain_path = main_cc
+        else:
+            self.toolchain_path = find_executable("arm-none-eabi-gcc") or ''
+
     def parse_dependencies(self, dep_path):
         dependencies = []
         buff = open(dep_path).readlines()
diff --git a/tools/toolchains/iar.py b/tools/toolchains/iar.py
index dac3b4852d2..ca41f845b26 100644
--- a/tools/toolchains/iar.py
+++ b/tools/toolchains/iar.py
@@ -17,6 +17,7 @@
 import re
 from os import remove
 from os.path import join, exists, dirname, splitext, exists
+from distutils.spawn import find_executable
 
 from tools.toolchains import mbedToolchain, TOOLCHAIN_PATHS
 from tools.hooks import hook_tool
@@ -50,6 +51,12 @@ def __init__(self, target, options=None, notify=None, macros=None, silent=False,
             cpuchoice = "Cortex-M7"
         else:
             cpuchoice = target.core
+
+        if not TOOLCHAIN_PATHS['IAR']:
+            exe =  find_executable('iccarm')
+            if exe:
+                TOOLCHAIN_PATHS['IAR'] = dirname(dirname(exe))
+
         # flags_cmd are used only by our scripts, the project files have them already defined,
         # using this flags results in the errors (duplication)
         # asm accepts --cpu Core or --fpu FPU, not like c/c++ --cpu=Core
@@ -101,6 +108,8 @@ def __init__(self, target, options=None, notify=None, macros=None, silent=False,
         self.ar = join(IAR_BIN, "iarchive")
         self.elf2bin = join(IAR_BIN, "ielftool")
 
+        self.toolchain_path = TOOLCHAIN_PATHS['IAR']
+
     def parse_dependencies(self, dep_path):
         return [(self.CHROOT if self.CHROOT else '')+path.strip() for path in open(dep_path).readlines()
                 if (path and not path.isspace())]