diff --git a/.github/workflows/matrix-and-codecov-on-merge-to-main.yml b/.github/workflows/matrix-and-codecov-on-merge-to-main.yml
deleted file mode 100644
index 3114aa2..0000000
--- a/.github/workflows/matrix-and-codecov-on-merge-to-main.yml
+++ /dev/null
@@ -1,62 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches:
-      - main
-  release:
-    types:
-      - prereleased
-      - published
-  workflow_dispatch:
-
-jobs:
-  matrix-coverage:
-    defaults:
-      run:
-        shell: bash -l {0}
-
-    runs-on: ${{ matrix.os }}
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-latest, windows-latest, macos-13, macos-14]
-        python-version: ["3.11", "3.12", "3.13"]
-    env:
-      LATEST_PYTHON_VERSION: "3.13"
-    steps:
-      - name: Check out diffpy.labpdfproc
-        uses: actions/checkout@v4
-
-      - name: Initialize miniconda
-        uses: conda-incubator/setup-miniconda@v3
-        with:
-          activate-environment: test
-          auto-update-conda: true
-          environment-file: environment.yml
-          auto-activate-base: false
-          python-version: ${{ matrix.python-version }}
-
-      - name: Conda config
-        run: >-
-          conda config --set always_yes yes
-          --set changeps1 no
-
-      - name: Install diffpy.labpdfproc and requirements
-        run: |
-          conda install --file requirements/tests.txt
-          conda install --file requirements/conda.txt
-          pip install gooey
-          python -m pip install . --no-deps
-
-      - name: Validate diffpy.labpdfproc
-        run: |
-          pytest --cov
-          coverage report -m
-          codecov
-
-      - name: Upload coverage to Codecov
-        if: matrix.os == 'ubuntu-latest' && matrix.python-version == env.LATEST_PYTHON_VERSION
-        uses: codecov/codecov-action@v4
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
diff --git a/docs/source/api/diffpy.labpdfproc.rst b/docs/source/api/diffpy.labpdfproc.rst
index 1bcc98d..a3f53e1 100644
--- a/docs/source/api/diffpy.labpdfproc.rst
+++ b/docs/source/api/diffpy.labpdfproc.rst
@@ -1,9 +1,7 @@
 :tocdepth: -1
 
-|title|
-=======
-
-.. |title| replace:: diffpy.labpdfproc package
+diffpy.labpdfproc package
+=========================
 
 .. automodule:: diffpy.labpdfproc
     :members:
@@ -14,17 +12,33 @@ Subpackages
 -----------
 
 .. toctree::
-   diffpy.labpdfproc.example_package
+    :titlesonly:
+
+    diffpy.labpdfproc.data
 
 Submodules
 ----------
 
-|module|
---------
+diffpy.labpdfproc.functions module
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. automodule:: diffpy.labpdfproc.functions
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
+diffpy.labpdfproc.tools module
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. automodule:: diffpy.labpdfproc.tools
+    :members:
+    :undoc-members:
+    :show-inheritance:
 
-.. |module| replace:: diffpy.labpdfproc.example_submodule module
+diffpy.labpdfproc.labpdfprocapp module
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-.. automodule:: diffpy.labpdfproc.example_submodule
+.. automodule:: diffpy.labpdfproc.labpdfprocapp
     :members:
     :undoc-members:
     :show-inheritance:
diff --git a/docs/source/examples/example-data/CeO2_635um_zscan_200umSlit_chanClose_exported.xy b/docs/source/examples/example-data/CeO2_635um_zscan.xy
similarity index 100%
rename from docs/source/examples/example-data/CeO2_635um_zscan_200umSlit_chanClose_exported.xy
rename to docs/source/examples/example-data/CeO2_635um_zscan.xy
diff --git a/docs/source/examples/labpdfprocapp-example.rst b/docs/source/examples/labpdfprocapp-example.rst
index a553c8f..c33cadf 100644
--- a/docs/source/examples/labpdfprocapp-example.rst
+++ b/docs/source/examples/labpdfprocapp-example.rst
@@ -10,121 +10,206 @@ to apply absorption correction to your 1D diffraction data using the command-lin
 Check ``labpdfproc --help`` for more information.
 A graphical user interface (GUI) is also available and is designed to be intuitive and easy to use.
 
+There are three ways to correct dirraction data within ``diffpy.labpdfproc``, these are,
 
-1. To use this application, you will need:
-(1) your input diffraction data file(s), and (2) information required to compute the muD value.
-To launch the GUI, use ``labpdfproc`` or ``labpdfproc --gui``.
-Note that the GUI is currently not supported on Python 3.13.
+1. ``labpdfproc mud``: Provide the diffraction data file(s) and muD value directly.
+2. ``labpdfproc zscan``: Provide the diffraction data file(s) and a z-scan file, which will be used to calculate the muD value.
+3. ``labpdfproc sample``: Provide the diffraction data file(s) and information about the sample to calculate the theoretical muD value.
 
+We will go through all three methods in this tutorial.
 
-2. Here we first provide a basic CLI example.
-Assume you have an uncorrected diffraction data file named ``zro2_mo.xy`` in the current directory
-with a muD of 2.5 on the two-theta x-axis. Then the minimum command would be:
+.. admonition:: Example Data
 
-.. code-block:: python
+    Example data for these examples can be found at: https://github.com/diffpy/diffpy.labpdfproc/tree/main/docs/source/examples/example-data
 
-    labpdfproc zro2_mo.xy --mud 2.5
 
+Launching the Graphical User Interface (GUI)
+--------------------------------------------
 
-3. You must provide at least one file path, and filepath(s) should immediately follow ``labpdfproc``.
+To launch the GUI, run one of the following commands in your terminal,
 
-To process multiple files at once in the CLI, separate each file path with a whitespace.
-In general, avoid spaces in filenames, but if necessary, enclose them in quotes; otherwise, quotes are optional.
-For example, the following is a valid and more complex CLI command:
+.. code-block:: bash
 
-.. code-block:: python
+   labpdfproc
+   labpdfproc --gui
 
-    labpdfproc "SiO2 uncorrected.xy" input_dir file_list.txt ./*.chi data* --mud 2.5
+.. note:: Note that the GUI is currently not supported on Python>=3.12.
 
-This command will process ``"SiO2 uncorrected.xy"``,
-all files in the ``input_dir`` directory, all files listed in ``file_list.txt``,
-all ``.chi`` files in the current directory, and all files matching the pattern ``data``,
-using a muD value of 2.5.
-Check ``labpdfproc --help`` to see all supported file types.
+This will open the GUI, which should look something like,
 
-In the GUI, you can select multiple individual files via the file browser, but not entire directories.
-To include directories, you can either:
-(1) create a text file named ``file_list.txt`` containing the desired paths and load it,
-(2) manually select all files in a folder, or
-(3) enter paths manually separated by a colon with no spaces.
+.. image:: ../img/labpdfproc-gui.jpeg
+   :align: center
 
-We will now continue using ``zro2_mo.xy`` as the example input throughout the rest of this tutorial.
+Below we will go through all the commands using the CLI, but the same principles apply to the GUI.
 
+.. note:: The first time you run any of the below commands,
+    you will be prompted to enter your name, email, and ORCID. This will be
+    appended to metadata in the output file header for reproducibility and tracking purposes.
 
-4. The muD value is required for absorption correction, and you can specify it in one of the four ways:
 
-.. code-block:: python
+``labpdfproc mud`` Command
+---------------------------
 
-    # Option 1: Manual value
-    labpdfproc zro2_mo.xy --mud 2.5
-    # Option 2: From a z-scan file
-    labpdfproc zro2_mo.xy -z zscan.xy
-    # Option 3: Using sample mass density
-    labpdfproc zro2_mo.xy -d ZrO2,17.45,1.2
-    # Option 4: Using packing fraction
-    labpdfproc zro2_mo.xy -p ZrO2,17.45,0.2
+If you know the muD value for your sample, you can use the ``labpdfproc mud``
+command to apply absorption correction directly.
 
-Note that you can only use one method at a time. The following examples are not allowed:
+To see all the options for this command, type,
 
-.. code-block:: python
+.. code-block:: bash
 
-    labpdfproc zro2_mo.xy --mud 2.5 -z zscan.xy
-    labpdfproc zro2_mo.xy --mud 2.5 -d ZrO2,17.45,1.2
+    labpdfproc mud -h
 
-If the packing fraction option is not supported at the moment, you can approximate the sample mass density as:
-``mass density = packing fraction * material density``, where the material density can be looked up manually.
+To run the correction, specify the path to your diffraction data file(s) and the muD value,
 
+.. code-block:: bash
 
-5. You can specify the wavelength in two ways:
+    labpdfproc mud <diffraction-data-file.xy> <mud>
+    labpdfproc mud zro2_mo.xy 2.5
 
-.. code-block:: python
+If the flag ``--wavelength`` is not specified, the program will attempt to fetch
+the wavelength from a configuration file.
+If the wavelength is not found in the configuration file, a ``ValueError``
+will be raised, prompting you to provide the wavelength either through the CLI or the configuration file.
 
-    # Option 1: Manually enter wavelength
-    labpdfproc zro2_mo.xy --mud 2.5 -w 0.71303
-    # Option 2: Use a known anode type
-    labpdfproc zro2_mo.xy --mud 2.5 -a Mo
+To provide the wavelength through the CLI, you can use the ``-w`` or ``--wavelength`` flag followed by the wavelength value in angstroms or the X-ray source.
+For example,
 
-Do not use both ``-w`` and ``-a`` at the same time. For example:
+.. code-block:: bash
 
-.. code-block:: python
+    labpdfproc mud zro2_mo.xy 2.5 -w 0.71303
+    labpdfproc mud zro2_mo.xy 2.5 -w Mo
 
-    labpdfproc zro2_mo.xy --mud 2.5 -w 0.71303 -a Mo
+This will then save the corrected file in the same directory as the input file with the name ``zro2_mo_corrected.chi``.
 
-is not valid. This is to avoid confusion when wavelength conflicts with anode type.
-To avoid retyping, you can save your wavelength or anode type in a diffpy configuration file.
-See full instructions at https://www.diffpy.org/diffpy.labpdfproc/examples/tools_example.html.
+To save the correction file, specify the ``-c`` or ``--output-correction`` flag,
 
+.. code-block:: bash
 
-6. You are also encouraged to provide your information (name, email, and orcid) for reproducibility:
+    labpdfproc mud zro2_mo.xy 2.5 -w 0.71303 -c
 
-.. code-block:: python
+This will then save the correction file in the same directory as the input file with the name ``zro2_mo_cve.chi``.
 
-    labpdfproc zro2_mo.xy --mud 2.5 -n Joe -e Joe@email.com --orcid 0000-0000-0000-0000
+``labpdfproc zscan`` Command
+----------------------------
 
+The ``labpdfproc zscan`` command allows you to calculate the muD value from a z-scan file and apply absorption correction to your diffraction data.
+For more information on what a z-scan is, please see the "Examples --> Linear Absorption Coefficient Examples"
+section in the ``diffpy.utils`` documentation: https://www.diffpy.org/diffpy.utils/examples/mu_calc_examples.html.
 
-Alternatively, you can enter this information during the interactive prompts
-or save it in your diffpy configuration file.
-For more details, refer to https://www.diffpy.org/diffpy.utils/examples/tools_example.html.
+To see the options for this command, type,
 
+.. code-block:: bash
 
-7. You can further customize the diffraction correction process using the following options:
+    labpdfproc zscan -h
 
-- Choose xtype: use ``-x`` to specify your input data's xtype, which will be used for the output.
-- Select correction method: use ``-m`` to choose between "brute_force" or "polynomial_interpolation" (faster and preferred for muD 0.5-7).
-- Specify output directory: use ``-o`` to save the corrected file(s) to a specific folder.
-- Add custom metadata: use ``-u`` to provide key-value pair for information tracking (e.g., experimental details).
-- Output the cve file: use ``-c`` to export the cve file along with the corrected data.
-- Overwrite existing files: use ``-f`` to replace any previous corrected files with the same names.
+To run this command, provide the path to your diffraction data file(s) and the z-scan file,
 
+.. code-block:: bash
 
-8. To summarize, a full command might look like this:
+    labpdfproc zscan <diffraction-data-file.xy> <zscan-file.xy>
+    labpdfproc zscan CeO2_635um_accum_0.xy CeO2_635um_zscan.xy
 
-.. code-block:: python
+Like the ``labpdfproc mud`` command, you can also specify the
+wavelength or source type using the ``-w`` flag if it's not found in the configuration file,
 
-    labpdfproc zro2_mo.xy --mud 2.5 -w 0.71303 -n Joe -x q -m brute_force -o results -u "facility=NSLS II" beamline=28ID-2 -c -f
+.. code-block:: bash
 
-After running the command, check your output folder (in this case, ``results``)
-for the corrected data file and cve file (if ``-c`` was used).
-In this example, the corrected and cve files are called ``zro2_mo_corrected.chi`` and ``zro2_mo_cve.chi``.
-The headers include all the arguments you provided
-—such as diffraction settings, personal information, and metadata—making it easy to track your analysis.
+    labpdfproc zscan CeO2_635um_accum_0.xy CeO2_635um_zscan.xy -w 0.71303
+    labpdfproc zscan CeO2_635um_accum_0.xy CeO2_635um_zscan.xy -w Mo
+
+This will save the corrected file in the same directory as the input file with the name ``CeO2_635um_accum_0.chi``.
+
+To save the correction file, specify the ``-c`` or ``--output-correction`` flag,
+
+.. code-block:: bash
+
+    labpdfproc zscan CeO2_635um_accum_0.xy CeO2_635um_zscan.xy -w 0.71303 -c
+
+This will then save the correction file in the same directory as the input file with the name ``CeO2_635um_accum_0_cve.chi``.
+
+``labpdfproc sample`` Command
+-----------------------------
+
+The ``labpdfproc sample`` command allows you to calculate the muD value from information
+about your sample and apply absorption correction to your diffraction data.
+
+To see the options for this command, type,
+
+.. code-block:: bash
+
+    labpdfproc sample -h
+
+To run this command, provide the path to your diffraction data file(s) along with:
+
+1) ``sample_composition``: The chemical formula of your sample.
+2) ``sample_mass_density``: The mass density of your sample in g/cm^3. If you don't know the mass density, a good approximation is typically ~1/3 of the theoretical packing fraction.
+3) ``diameter``: The outer diameter of your capillary.
+
+.. code-block:: bash
+
+    labpdfproc sample <diffraction-data-file.xy> <sample_composition> <sample_mass_density> <diameter>
+    labpdfproc sample zro2_mo.xy ZrO2 17.45 1.2
+
+Once again, you can specify the wavelength or source type using the ``-w`` flag if it's not found in the configuration file,
+
+.. code-block:: bash
+
+    labpdfproc sample zro2_mo.xy ZrO2 17.45 1.2 -w 0.71303
+    labpdfproc sample zro2_mo.xy ZrO2 17.45 1.2 -w Mo
+
+This will save the corrected file in the same directory as the input file with the name ``zro2_mo.chi``.
+
+To save the correction file, specify the ``-c`` or ``--output-correction`` flag,
+
+.. code-block:: bash
+
+    labpdfproc sample zro2_mo.xy ZrO2 17.45 1.2 -w 0.71303 -c
+
+This will then save the correction file in the same directory as the input file with the name ``zro2_mo_cve.chi``.
+
+Additional CLI options
+----------------------
+
+Below is a summary of all the additional flags that can be used with all three commands,
+
+- ``-h, --help``
+  Show this help message and exit.
+
+- ``-w, --wavelength WAVELENGTH``
+  X-ray wavelength in angstroms (numeric) or X-ray source name.
+  Allowed: ``Ag``, ``AgKa1``, ``AgKa1Ka2``, ``Cu``, ``CuKa1``, ``CuKa1Ka2``, ``Mo``, ``MoKa1``, ``MoKa1Ka2``.
+  Will be loaded from config files if not specified.
+
+- ``-x, --xtype XTYPE``
+  X-axis type (default: ``tth``). Allowed values: ``angle``, ``tth``, ``twotheta``, ``2theta``, ``d``, ``dspace``, ``q``.
+
+- ``-m, --method {brute_force, polynomial_interpolation}``
+  Method for cylindrical volume element (CVE) calculation (default: ``polynomial_interpolation``).
+  Allowed methods: ``brute_force``, ``polynomial_interpolation``.
+
+- ``-o, --output-directory OUTPUT_DIRECTORY``
+  Directory to save corrected files (created if needed). Defaults to current directory.
+
+- ``-f, --force``
+  Overwrite existing files.
+
+- ``-c, --output-correction``
+  Also output the absorption correction to a separate file.
+
+- ``-u, --user-metadata KEY=VALUE [KEY=VALUE ...]``
+  Specify key-value pairs to be loaded into metadata. Format: ``key=value``.
+  - Separate multiple pairs with whitespace.
+  - No spaces before or after ``=``.
+  - Avoid using ``=`` in keys. Only the first ``=`` separates key and value.
+  - If a key or value contains whitespace, enclose it in quotes.
+    Examples:
+    ``facility='NSLS II', beamline=28ID-2, 'favorite color'=blue``.
+
+- ``--username USERNAME``
+  Your name (optional, for dataset credit). Will be loaded from config files if not specified.
+
+- ``--email EMAIL``
+  Your email (optional, for dataset credit). Will be loaded from config files if not specified.
+
+- ``--orcid ORCID``
+  Your ORCID ID (optional, for dataset credit). Will be loaded from config files if not specified.
diff --git a/docs/source/examples/tools-example.rst b/docs/source/examples/tools-example.rst
index 674d244..7291658 100644
--- a/docs/source/examples/tools-example.rst
+++ b/docs/source/examples/tools-example.rst
@@ -20,15 +20,13 @@ You can do this in one of the following four ways:
     # Option 2: From a z-scan file
     args = Namespace(z_scan_file="zscan.xy")
     # Option 3: Using sample mass density
-    args = Namespace(theoretical_from_density="ZrO2,17.45,1.2")
-    # Option 4: Using packing fraction
-    args = Namespace(theoretical_from_packing="ZrO2,17.45,0.3")
+    args = Namespace(sample_composition="ZrO2", sample_mass_density="17.45", diameter="1.2")
     # Set and view the computed mu*D value
     args = set_mud(args)
     print(args.mud)
 
 
-2. Next, we load the input files for correction using ``set_input_lists(args)``:
+1. Next, we load the input files for correction using ``set_input_lists(args)``:
 
 .. code-block:: python
 
@@ -59,24 +57,13 @@ If no output directory is specified, it defaults to the current working director
     # Option 1: Specify wavelength directly
     args = Namespace(wavelength=0.7)
     # Option 2: Use a valid anode type
-    args = Namespace(anode_type="Mo")
+    args = Namespace(wavelength="Mo")
     args = set_wavelength(args)
 
 Note that you should specify either a wavelength or an anode type, not both, to avoid conflicts.
 If you provide an anode type, the corresponding wavelength will be retrieved from global parameters.
 You may use ``labpdfproc --help`` to view a list of valid anode types.
 If neither is given, it's only acceptable if the input diffraction data is already on a two-theta grid.
-To simplify workflows and avoid re-entering it every time,
-we recommend saving the wavelength or anode type to a diffpy config file. For example:
-
-.. code-block:: python
-
-    from pathlib import Path
-    import json
-    home_dir = Path.home()
-    wavelength_data = {"wavelength": 0.3}
-    with open(home_dir / "diffpyconfig.json", "w") as f:
-        json.dump(wavelength_data, f)
 
 To set the x-axis type (xtype) for your diffraction data:
 
@@ -88,7 +75,7 @@ To set the x-axis type (xtype) for your diffraction data:
 This sets the xtype to ``tth``. Other valid options including ``q`` and ``d`` spacing.
 
 
-5. Finally, we load user metadata, user information, and package information into ``args``.
+1. Finally, we load user metadata, user information, and package information into ``args``.
 To load metadata, pass key-value pairs as a list:
 
 .. code-block:: python
@@ -137,3 +124,19 @@ Using the function ``load_metadata(args, filepath)``
 requires both the ``argument.Namespace`` and the current input file path.
 For more details about working with diffraction objects and how they are written to output files, see
 https://www.diffpy.org/diffpy.utils/examples/diffraction_objects_example.html.
+
+
+Creating ``diffpyconfig.json`` file
+-----------------------------------
+
+To simplify workflows and avoid re-entering it every time,
+we recommend saving the wavelength or anode type to a diffpy config file. For example,
+
+.. code-block:: python
+
+    from pathlib import Path
+    import json
+    home_dir = Path.home()
+    wavelength_data = {"wavelength": 0.3}
+    with open(home_dir / "diffpyconfig.json", "w") as f:
+        json.dump(wavelength_data, f)
diff --git a/docs/source/img/.placeholder b/docs/source/img/.placeholder
deleted file mode 100644
index e69de29..0000000
diff --git a/docs/source/img/labpdfproc-gui.jpeg b/docs/source/img/labpdfproc-gui.jpeg
new file mode 100644
index 0000000..9dc8de8
Binary files /dev/null and b/docs/source/img/labpdfproc-gui.jpeg differ
diff --git a/news/doc0.3.0.rst b/news/doc0.3.0.rst
new file mode 100644
index 0000000..b0af63d
--- /dev/null
+++ b/news/doc0.3.0.rst
@@ -0,0 +1,23 @@
+**Added:**
+
+* Added documentation for new CLI updates.
+
+**Changed:**
+
+* Return a ``ValueError`` if no wavelength is found on config file or if its not specified.
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>
diff --git a/src/diffpy/labpdfproc/labpdfprocapp.py b/src/diffpy/labpdfproc/labpdfprocapp.py
index e5575ec..e5dd808 100644
--- a/src/diffpy/labpdfproc/labpdfprocapp.py
+++ b/src/diffpy/labpdfproc/labpdfprocapp.py
@@ -1,4 +1,5 @@
 import argparse
+import os
 import sys
 
 from gooey import Gooey, GooeyParser
@@ -15,6 +16,17 @@
 from diffpy.utils.parsers import load_data
 
 
+def _running_in_gui():
+    """Determine if the application is running in a GUI environment.
+
+    This function checks if the standard output (sys.stdout) is
+    connected to a terminal. If not, it assumes the application is
+    running in a GUI environment, such as when launched by Gooey. This
+    is used to prevent ANSI escape sequences from rendering in the GUI.
+    """
+    return not sys.stdout.isatty()
+
+
 def _add_common_args(parser, use_gui=False):
     parser.add_argument(
         "-w",
@@ -172,6 +184,13 @@ def apply_absorption_correction(args):
 
 def create_parser(use_gui=False):
     Parser = GooeyParser if use_gui else argparse.ArgumentParser
+
+    # Force no colors when gui is running to avoid ANSI escape codes
+    # in Gooey output
+    if use_gui or _running_in_gui():
+        os.environ["NO_COLOR"] = "1"
+        os.environ["CLICOLOR"] = "0"
+
     parser = Parser(
         prog="labpdfproc",
         description=(
diff --git a/src/diffpy/labpdfproc/tools.py b/src/diffpy/labpdfproc/tools.py
index 01c4a0e..2aa6754 100644
--- a/src/diffpy/labpdfproc/tools.py
+++ b/src/diffpy/labpdfproc/tools.py
@@ -224,29 +224,43 @@ def load_wavelength_from_config_file(args):
     args : argparse.Namespace
         The updated arguments with the updated wavelength and anode type.
     """
-    global_config = _load_config(Path().home() / "diffpyconfig.json")
-    local_config = _load_config(Path().cwd() / "diffpyconfig.json")
-    local_has_data = local_config and "wavelength" in local_config
-    global_has_data = global_config and "wavelength" in global_config
-    if not local_has_data and not global_has_data:
-        print(
-            "No configuration file was found containing information "
-            "about the wavelength or anode type. \n"
-            "You can add the wavelength or anode type "
-            "to a configuration file on the current computer "
-            "and it will be automatically associated with "
-            "subsequent diffpy data by default. \n"
-            "You will only have to do that once. \n"
-            "For more information, please refer to www.diffpy.org/"
-            "diffpy.labpdfproc/examples/toolsexample.html"
-        )
+
     if args.wavelength is not None:
         return normalize_wavelength(args)
-    config = local_config if local_has_data else global_config
-    if config:
-        args.wavelength = config.get("wavelength")
+
+    global_config_file = _load_config(Path().home() / "diffpyconfig.json")
+    local_config_file = _load_config(Path().cwd() / "diffpyconfig.json")
+    config_file = None
+    if (
+        isinstance(local_config_file, dict)
+        and "wavelength" in local_config_file
+    ):
+        config_file = local_config_file
+    elif (
+        isinstance(global_config_file, dict)
+        and "wavelength" in global_config_file
+    ):
+        config_file = global_config_file
+    if config_file is not None:
+        args.wavelength = config_file.get("wavelength")
         return normalize_wavelength(args)
-    return args
+    else:
+        raise ValueError(
+            "\nThe wavelength was not specified and no "
+            "configuration file 'diffpyconfig.json' containing "
+            "the wavelength or X-ray source was found in either the "
+            "local or home directories. Either specify the wavelength "
+            "or source using the -w/--wavelength option or "
+            "create a configuration file.\n\n"
+            "You can add the wavelength or anode type to a "
+            "configuration file on this computer. Once created, it "
+            "will be automatically used for subsequent diffpy data "
+            "by default, and you will only need to do this once.\n\n"
+            "For detailed instructions on creating the configuration "
+            "file, please refer to:\n"
+            "https://www.diffpy.org/diffpy.labpdfproc/examples/"
+            "toolsexample.html"
+        )
 
 
 def set_wavelength(args):
diff --git a/tests/test_tools.py b/tests/test_tools.py
index 05ff84d..e7a137e 100644
--- a/tests/test_tools.py
+++ b/tests/test_tools.py
@@ -311,6 +311,74 @@ def test_load_wavelength_from_config_file_with_local_conf_file(
     assert actual_args.wavelength == expected["wavelength"]
 
 
+@pytest.mark.parametrize(
+    "local_config, home_config",
+    [
+        # C1: no config files exist
+        # expected: raise ValueError
+        (None, None),
+        # C2: local config is empty, no home config
+        # expected: raise ValueError
+        ({}, None),
+        # C3: no local config, home config is empty
+        # expected: raise ValueError
+        (None, {}),
+        # C4: both config files are empty
+        # expected: raise ValueError
+        ({}, {}),
+    ],
+)
+def test_load_wavelength_from_config_file_without_conf_files_bad(
+    mocker,
+    user_filesystem,
+    local_config,
+    home_config,
+):
+    # User tries to correct data without specifying wavelength and
+    # no config files
+    # with wavelength exist -- expected to raise ValueError
+    cwd = Path(user_filesystem)
+    home_dir = cwd / "home_dir"
+    mocker.patch("pathlib.Path.home", return_value=home_dir)
+    os.chdir(cwd)
+
+    local_config_file = cwd / "diffpyconfig.json"
+    if local_config_file.exists():
+        local_config_file.unlink()
+    home_config_file = home_dir / "diffpyconfig.json"
+    if home_config_file.exists():
+        home_config_file.unlink()
+
+    if local_config is not None:
+        with open(local_config_file, "w") as f:
+            json.dump(local_config, f)
+    if home_config is not None:
+        with open(home_config_file, "w") as f:
+            json.dump(home_config, f)
+
+    cli_inputs = ["mud", "data.xy", "2.5"]
+    actual_args = get_args_cli(cli_inputs)
+
+    msg = re.escape(
+        "\nThe wavelength was not specified and no "
+        "configuration file 'diffpyconfig.json' containing "
+        "the wavelength or X-ray source was found in either the "
+        "local or home directories. Either specify the wavelength "
+        "or source using the -w/--wavelength option or "
+        "create a configuration file.\n\n"
+        "You can add the wavelength or anode type to a "
+        "configuration file on this computer. Once created, it "
+        "will be automatically used for subsequent diffpy data "
+        "by default, and you will only need to do this once.\n\n"
+        "For detailed instructions on creating the configuration "
+        "file, please refer to:\n"
+        "https://www.diffpy.org/diffpy.labpdfproc/examples/"
+        "toolsexample.html"
+    )
+    with pytest.raises(ValueError, match=msg):
+        load_wavelength_from_config_file(actual_args)
+
+
 @pytest.mark.parametrize(
     "inputs, expected",
     [
@@ -318,8 +386,6 @@ def test_load_wavelength_from_config_file_with_local_conf_file(
         # expect to return args without modification.
         # This test only checks loading behavior,
         # not value validation (which is handled by `set_wavelength`).
-        # C1: no args
-        ([], {"wavelength": None}),
         # C1: wavelength provided
         (["--wavelength", "0.25"], {"wavelength": 0.25}),
         # C2: anode type provided