Document the existence of Plecos (the tool)

content/concepts/tools.md

@@ -5,7 +5,9 @@ description: Tools and examples for developing with Ocean Protocol.
 
 ## Tools
 
-Coming soon!
+[Plecos](https://github.com/oceanprotocol/plecos) is a Python tool to check metadata (a JSON file) to see if it conforms to the [OEP8 schema](https://github.com/oceanprotocol/OEPs/tree/master/8). Users can use Plecos to check their metadata before sending it to an Aquarius instance.
+
+<repo name="Plecos"></repo>
 
 ## Examples
 

data/repositories.yml

@@ -28,6 +28,7 @@
         - name: API reference
           url: /references/squid-py/
     - name: squid-java
+    - name: Plecos
 
 - group: OceanDB
   items: