Document the validate and stats commands

README.md

@@ -15,6 +15,38 @@ Extract the archive and place the `stac` executable somewhere on your path.  See
 
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+### CLI Usage
+
+Run `stac help` to see a full list of commands and their arguments.  The primary `stac` commands are documented below.
+
+#### stac validate
+
+The `stac validate` command crawls STAC resources and validates them against the appropriate schema.
+
+Example use:
+
+    stac validate --entry path/to/catalog.json
+
+The `--entry` can be a file path or URL pointing to a catalog, collection, or item.  By default, all catalogs, collections, and items linked from the entry point will be validated.  Use the `--no-recursion` option to validate a single resource without crawling to linked resources.  See `stac validate --help` for a full list of supported options.
+
+#### stac stats
+
+The `stac stats` command crawls STAC resources and prints out counts of resource type, versions, extensions, asset types, and conformance classes (for API endpoints).
+
+Example use:
+
+    stac stats --entry path/to/catalog.json
+
+The `--entry` can be a file path or URL pointing to a catalog, collection, or item.  The stats output is a JSON object with top-level properties for catalog, collection, and item stats.
+
+The structure of the output conforms with the schema of the [STAC Stats extension](https://github.com/stac-extensions/stats), so the results can be added to a STAC entrypoint to provide stats on child catalogs, collections, and items.  When generating output to be added to a catalog or collection, you don't want to include counts for the entrypoint itself in the reported statistics.  The `--exclude-entry` flag is used to report statistics on resources linked from the entry but not on the entry itself.
+
+To generate statistics for the STAC Stats extension, run the following:
+
+    stac stats --entry path/to/catalog.json --exclude-entry
+
+Paste the resulting top-level `stats:*` prefixed properties into your `catalog.json` and add the extension identifier to your catalog's `stac_extensions` property as described by the [STAC Stats extension](https://github.com/stac-extensions/stats).
+
 ## Library Use
 
 Requires Go >= 1.18