diff --git a/tests/test_decoder.py b/tests/test_decoder.py
index 8ec0c46..f808fc5 100644
--- a/tests/test_decoder.py
+++ b/tests/test_decoder.py
@@ -43,6 +43,19 @@
     )
 assert _DUPLICATE_WORKFLOW_VARIABLE_NAMES_WORKFLOW
 
+_STEP_SPECIFICATION_VARIABLE_NAMES_WORKFLOW_FILE: str = os.path.join(
+    os.path.dirname(__file__),
+    "workflow-definitions",
+    "step-specification-variable-names.yaml",
+)
+with open(
+    _STEP_SPECIFICATION_VARIABLE_NAMES_WORKFLOW_FILE, "r", encoding="utf8"
+) as workflow_file:
+    _STEP_SPECIFICATION_VARIABLE_NAMES_WORKFLOW: Dict[str, Any] = yaml.safe_load(
+        workflow_file
+    )
+assert _STEP_SPECIFICATION_VARIABLE_NAMES_WORKFLOW
+
 
 def test_validate_schema_for_minimal():
     # Arrange
@@ -110,6 +123,16 @@ def test_validate_schema_for_python_simple_molprops():
     assert error is None
 
 
+def test_validate_schema_for_step_specification_variable_names():
+    # Arrange
+
+    # Act
+    error = decoder.validate_schema(_STEP_SPECIFICATION_VARIABLE_NAMES_WORKFLOW)
+
+    # Assert
+    assert error is None
+
+
 def test_get_workflow_variables_for_smiple_python_molprops():
     # Arrange
 
diff --git a/tests/workflow-definitions/duplicate-step-names.yaml b/tests/workflow-definitions/duplicate-step-names.yaml
index 426c6fc..f89d610 100644
--- a/tests/workflow-definitions/duplicate-step-names.yaml
+++ b/tests/workflow-definitions/duplicate-step-names.yaml
@@ -4,8 +4,12 @@ kind-version: "2024.1"
 name: duplicate-step-names
 steps:
 - name: step-1
-  specification: >-
-    {}
+  specification:
+    collection: a
+    job: b
+    version: '1.0.0'
 - name: step-1
-  specification: >-
-    {}
+  specification:
+    collection: a
+    job: b
+    version: '2.0.0'
diff --git a/tests/workflow-definitions/duplicate-workflow-variable-names.yaml b/tests/workflow-definitions/duplicate-workflow-variable-names.yaml
index bfca24a..7649404 100644
--- a/tests/workflow-definitions/duplicate-workflow-variable-names.yaml
+++ b/tests/workflow-definitions/duplicate-workflow-variable-names.yaml
@@ -17,16 +17,13 @@ variables:
 steps:
 - name: step1
   description: Add column 1
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "rdkit-molprops",
-      "version": "1.0.0",
-      "variables": {
-        "name": "col1",
-        "value": 123
-      }
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: rdkit-molprops
+    version: "1.0.0"
+    variables:
+      name: "col1"
+      value: 123
   inputs:
   - input: inputFile
     from:
@@ -37,16 +34,13 @@ steps:
 
 - name: step2
   description: Add column 2
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "cluster-butina",
-      "version":"1.0.0",
-      "variables": {
-        "name":"col2",
-        "value":"999"
-      }
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: cluster-butina
+    version: "1.0.0"
+    variables:
+      name: "col2"
+      value: "999"
   inputs:
   - input: inputFile
     from:
diff --git a/tests/workflow-definitions/example-nop-fail.yaml b/tests/workflow-definitions/example-nop-fail.yaml
index b3bd36f..f265988 100644
--- a/tests/workflow-definitions/example-nop-fail.yaml
+++ b/tests/workflow-definitions/example-nop-fail.yaml
@@ -6,9 +6,7 @@ description: >-
   A workflow with one step that fails
 steps:
 - name: step-1
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "nop-fail",
-      "version": "1.0.0"
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: nop-fail
+    version: "1.0.0"
diff --git a/tests/workflow-definitions/example-smiles-to-file.yaml b/tests/workflow-definitions/example-smiles-to-file.yaml
index fea20c5..e543050 100644
--- a/tests/workflow-definitions/example-smiles-to-file.yaml
+++ b/tests/workflow-definitions/example-smiles-to-file.yaml
@@ -7,9 +7,7 @@ description: >-
   The step takes an input string and the Job creates a file from it.
 steps:
 - name: step-1
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "smiles-to-file",
-      "version": "1.0.0"
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: smiles-to-file
+    version: "1.0.0"
diff --git a/tests/workflow-definitions/example-two-step-nop.yaml b/tests/workflow-definitions/example-two-step-nop.yaml
index 1462e34..df64b9a 100644
--- a/tests/workflow-definitions/example-two-step-nop.yaml
+++ b/tests/workflow-definitions/example-two-step-nop.yaml
@@ -7,16 +7,12 @@ description: >-
   The steps do nothing, take no arguments, and simply return success.
 steps:
 - name: step-1
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "nop",
-      "version": "1.0.0"
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: nop
+    version: "1.0.0"
 - name: step-2
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "nop",
-      "version": "1.0.0"
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: nop
+    version: "1.0.0"
diff --git a/tests/workflow-definitions/minimal.yaml b/tests/workflow-definitions/minimal.yaml
index e8dcc53..d2dd2cb 100644
--- a/tests/workflow-definitions/minimal.yaml
+++ b/tests/workflow-definitions/minimal.yaml
@@ -4,5 +4,7 @@ kind-version: "2024.1"
 name: workflow-minimal
 steps:
 - name: step-1
-  specification: >-
-    {}
+  specification:
+    collection: a
+    job: b
+    version: "1.0.0"
diff --git a/tests/workflow-definitions/shortcut-example-1.yaml b/tests/workflow-definitions/shortcut-example-1.yaml
index 390ac58..a9446e7 100644
--- a/tests/workflow-definitions/shortcut-example-1.yaml
+++ b/tests/workflow-definitions/shortcut-example-1.yaml
@@ -6,23 +6,19 @@ description: The shortcut example 1 workflow
 steps:
 - name: example-1-step-1
   description: The first step
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "shortcut-example-1-process-a",
-      "version": "1.0.0"
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: shortcut-example-1-process-a
+    version: "1.0.0"
   outputs:
   - output: 'outputFile'
     as: 'a.sdf'
 - name: example-1-step-2
   description: The first step
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "shortcut-example-1-process-b",
-      "version": "1.0.0"
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: shortcut-example-1-process-b
+    version: "1.0.0"
   inputs:
   - input: 'inputFile'
     from:
diff --git a/tests/workflow-definitions/simple-python-molprops.yaml b/tests/workflow-definitions/simple-python-molprops.yaml
index 049a010..aeeeafe 100644
--- a/tests/workflow-definitions/simple-python-molprops.yaml
+++ b/tests/workflow-definitions/simple-python-molprops.yaml
@@ -17,16 +17,13 @@ variables:
 steps:
 - name: step1
   description: Add column 1
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "rdkit-molprops",
-      "version": "1.0.0",
-      "variables": {
-        "name": "col1",
-        "value": 123
-      }
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: rdkit-molprops
+    version: "1.0.0"
+    variables:
+      name: "col1"
+      value: 123
   inputs:
   - input: inputFile
     from:
@@ -37,16 +34,13 @@ steps:
 
 - name: step2
   description: Add column 2
-  specification: >-
-    {
-      "collection": "workflow-engine-unit-test-jobs",
-      "job": "cluster-butina",
-      "version":"1.0.0",
-      "variables": {
-        "name":"col2",
-        "value":"999"
-      }
-    }
+  specification:
+    collection: workflow-engine-unit-test-jobs
+    job: cluster-butina
+    version: "1.0.0"
+    variables:
+      name: "col2"
+      value: "999"
   inputs:
   - input: inputFile
     from:
diff --git a/tests/workflow-definitions/step-specification-variable-names.yaml b/tests/workflow-definitions/step-specification-variable-names.yaml
new file mode 100644
index 0000000..0a9bbca
--- /dev/null
+++ b/tests/workflow-definitions/step-specification-variable-names.yaml
@@ -0,0 +1,16 @@
+---
+kind: DataManagerWorkflow
+kind-version: "2024.1"
+name: step-variables
+description: Test a lot of variables whose format is supported
+steps:
+- name: step-1
+  specification:
+    collection: a
+    job: b
+    version: '1.0.0'
+    variables:
+      _a: 1
+      A-1: 2.0
+      a_14_: A string
+      A-Long_boolean_variable_Name: true
diff --git a/workflow/workflow-schema.yaml b/workflow/workflow-schema.yaml
index 68a62d2..07f018f 100644
--- a/workflow/workflow-schema.yaml
+++ b/workflow/workflow-schema.yaml
@@ -161,6 +161,42 @@ definitions:
     - output
     - as
 
+
+  # A step specification variable
+  # (there must be at least one if a variables block is defined).
+  # Typical variable syntax based on Python's definition of a variable
+  # but with the inclusion of 'hyphen' within the variable.
+  # The value of the variable (the object itself) is quite relaxed...
+  # it simply needs to be a string, number (integer or float), or boolean.
+  step-specification-variable:
+    type: object
+    additionalProperties: false
+    patternProperties:
+      '^[a-zA-Z_]{1}[a-zA-Z0-9_-]{0,79}$':
+        oneOf:
+        - type: string
+        - type: integer
+        - type: boolean
+    minProperties: 1
+
+  # Step specification
+  step-specification:
+    type: object
+    additionalProperties: false
+    properties:
+      collection:
+        type: string
+      job:
+        type: string
+      version:
+        type: string
+      variables:
+        $ref: "#/definitions/step-specification-variable"
+    required:
+    - collection
+    - job
+    - version
+
   # Steps (in a workflow)
   step:
     type: object
@@ -172,8 +208,7 @@ definitions:
         type: string
         description: A description of the step
       specification:
-        type: string
-        description: The Data Manager Job Specification, a JSON string
+        $ref: '#/definitions/step-specification'
       inputs:
         type: array
         items:
diff --git a/workflow/workflow_engine.py b/workflow/workflow_engine.py
index edff2ec..8d76bdd 100644
--- a/workflow/workflow_engine.py
+++ b/workflow/workflow_engine.py
@@ -22,7 +22,6 @@
 is executed, and it uses thew InstanceLauncher to launch the Job (a Pod) for each step.
 """
 
-import json
 import logging
 import sys
 from typing import Any, Dict, Optional
@@ -295,7 +294,7 @@ def _validate_step_command(
         # the keys "collection", "job", and "version". Here we assume that
         # the workflow definition has passed the RUN-level validation
         # which means we can get these values.
-        step_spec: dict[str, Any] = json.loads(step["specification"])
+        step_spec: dict[str, Any] = step["specification"]
         job_collection: str = step_spec["collection"]
         job_job: str = step_spec["job"]
         job_version: str = step_spec["version"]
@@ -466,7 +465,7 @@ def _launch(
             debug=rwf.get("debug"),
             launching_user_name=rwf["running_user"],
             launching_user_api_token=rwf["running_user_api_token"],
-            specification=json.loads(step["specification"]),
+            specification=step["specification"],
             specification_variables=variables,
             running_workflow_id=rwf_id,
             running_workflow_step_id=rwfs_id,
diff --git a/workflow/workflow_validator.py b/workflow/workflow_validator.py
index 60b668a..78198b8 100644
--- a/workflow/workflow_validator.py
+++ b/workflow/workflow_validator.py
@@ -1,6 +1,5 @@
 """The WorkflowEngine validation logic."""
 
-import json
 from dataclasses import dataclass
 from enum import Enum
 from typing import Any
@@ -96,40 +95,6 @@ def _validate_tag_level(
                 error_num=2,
                 error_msg=[f"Duplicate step names found: {', '.join(duplicate_names)}"],
             )
-        # Each step specification must be a valid JSON string.
-        # and contain properties for 'collection', 'job', and 'version'.
-        for step in workflow_definition["steps"]:
-            step_name = step["name"]
-            try:
-                specification = json.loads(step["specification"])
-            except json.decoder.JSONDecodeError as e:
-                return ValidationResult(
-                    error_num=3,
-                    error_msg=[
-                        f"Got JSONDecodeError decoding Step '{step_name}' specification: {e}"
-                    ],
-                )
-            except TypeError as e:
-                return ValidationResult(
-                    error_num=4,
-                    error_msg=[
-                        f"Got ValidationResult decoding Step '{step_name}' specification: {e}"
-                    ],
-                )
-            expected_keys: set[str] = {"collection", "job", "version"}
-            missing_keys: list[str] = []
-            missing_keys.extend(
-                expected_key
-                for expected_key in expected_keys
-                if expected_key not in specification
-            )
-            if missing_keys:
-                return ValidationResult(
-                    error_num=5,
-                    error_msg=[
-                        f"Step '{step_name}' specification is missing: {', '.join(missing_keys)}"
-                    ],
-                )
         # Workflow variables must be unique.
         duplicate_names = set()
         variable_names: set[str] = set()