Add initial ChemicalJSON documentation migrated from archived wiki

README.md

@@ -21,3 +21,10 @@ represntations for chemistry, and to document those representations more
 formally than has been done in the past.
 
 [Chemical_JSON]: http://wiki.openchemistry.org/Chemical_JSON
+
+## Documentation
+
+Project documentation is available in the [docs directory](./docs).
+This content is migrated from the archived Open Chemistry wiki and
+serves as a centralized reference until a dedicated documentation
+site is available.

docs/overview.md

@@ -0,0 +1,24 @@
+# ChemicalJSON
+
+## Purpose
+
+ChemicalJSON is a JSON-based format for representing chemical data
+in a structured and machine-readable way. It is designed to support
+storage, exchange, and processing of chemical information across
+different tools and programming languages.
+
+## Basic Structure
+
+A ChemicalJSON document typically includes:
+
+- Metadata such as molecule name and formula
+- Atomic information (elements, coordinates)
+- Optional properties such as unit cells, energies, or orbitals
+
+The format is designed to be extensible, allowing new properties
+to be added without breaking existing tools.
+
+## Examples
+
+See the [examples directory](../examples) for concrete examples of
+ChemicalJSON files, including small molecules and periodic systems.