diff --git a/tools/json/README.md b/tools/json/README.md
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+This folder contains files and tools for creating, modifying, and validating
+files in JSON format. This is work in progress while we are adding JSON
+support 
+
+# JSON file format validation.
+
+## JSON-Schema files
+
+We provide schema files for the file formats that LAMMPS supports following
+the specifications available on [JSON-Schema](https://json-schema.org) webpage.
+The following files are currently available.
+
+- `molecule-schema.json`  Schema file for the JSON format molecule files.
+
+These files provide a concise description of the hierarchy and supported fields
+in JSON file formats.  Thus they provide a detailed documentation and can also
+be used for validating JSON files.
+
+## Validation of JSON files
+
+There are multiple tools for JSON file validation available.  Here are instructions
+for how to use a tool called `check-jsonschema` which is available via
+[PyPi](https://pypi.org/).
+
+``` bash
+# Installation into a virtual environment.
+# Once installed only the activation should be needed
+python3 -m venv validate-json
+source validata-json/bin/activate
+pip install --upgrade pip
+pip install check-jsonschema
+
+# Validation of two molecule files "rxn1.json" and "twomols.json" with "molecule-schema.json"
+check-jsonschema --schemafile molecule-schema.json rxn1.json twomols.json
+```
+
+If the files are conforming there should be the output:
+```
+ok -- validation done
+```
+Otherwise details about the non-conforming fields are given.
+
+-------
+
+updated by Axel Kohlmeyer, 2025-05-22
diff --git a/tools/json/molecule-schema.json b/tools/json/molecule-schema.json
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+{
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "$id": "https://download.lammps.org/json/molecule-schema.json",
+    "type": "object",
+    "properties": {
+        "application": { "enum": ["LAMMPS"]},
+        "format": {"enum": ["molecule"]},
+        "revision": {
+            "type": "integer",
+            "minimum": 1,
+            "maximum": 1
+        },
+        "title": {"type": "string"},
+        "docs": {"type": "string"},
+        "schema": {"type": "string"},
+        "com": {"type": "array",
+                "prefixItems": [
+                    {"type": "number"},
+                    {"type": "number"},
+                    {"type": "number"}
+                ],
+                "items": false
+               },
+        "masstotal": {"type": "number"},
+        "body": {"type": "array",
+                "prefixItems": [
+                    {"type": "integer"},
+                    {"type": "integer"}
+                ],
+                "items": false
+               },
+        "inertia": {"type": "array",
+                "prefixItems": [
+                    {"type": "number"},
+                    {"type": "number"},
+                    {"type": "number"},
+                    {"type": "number"},
+                    {"type": "number"},
+                    {"type": "number"}
+                ],
+                "items": false
+               },
+        "coords": {
+            "type": "object",
+            "properties": {
+                "format": {
+                    "type": "array",
+                    "prefixItems": [
+                        {"enum": ["atom-id"]},
+                        {"enum": ["x"]},
+                        {"enum": ["y"]},
+                        {"enum": ["z"]}
+                    ],
+                    "items": false
+                },
+                "data": {
+                    "type": "array",
+                    "items": {
+                        "type": "array",
+                        "prefixItems": [
+                            {"type": "integer"},
+                            {"type": "number"},
+                            {"type": "number"},
+                            {"type": "number"}
+                        ],
+                        "items": false
+                    }
+                }
+            }
+        },
+        "types": {
+            "type": "object",
+            "properties": {
+                "format": {
+                    "type": "array",
+                    "items": {
+                        "type": "string"
+                    }
+                },
+                "data": {
+                    "type": "array",
+                    "items": {
+                        "type": "array",
+                        "prefixItems": [
+                            {"type": "number"},
+                            {"type": ["number", "string"]}
+                        ],
+                        "items": false
+                    }
+                }
+            }
+        },
+        "molecules": {
+            "type": "object",
+            "properties": {
+                "format": {
+                    "type": "array",
+                    "items": {
+                        "type": "string"
+                    }
+                },
+                "data": {
+                    "type": "array",
+                    "items": {
+                        "type": "array",
+                        "items": {
+                            "type": "number"
+                        }
+                    }
+                }
+            }
+        },
+        "charges": {
+            "type": "object",
+            "properties": {
+                "format": {
+                    "type": "array",
+                    "items": {
+                        "type": "string"
+                    }
+                },
+                "data": {
+                    "type": "array",
+                    "items": {
+                        "type": "array",
+                        "items": {
+                            "type": "number"
+                        }
+                    }
+                }
+            }
+        }
+    }
+}