Microsoft has suggested developers to start using the new Web API to develop new custom development. As they are planning to deprecate the 2011 endpoints sometime after CRM version 9 (We are on version 8 now!). Ref: https://msdn.microsoft.com/en-us/library/dn281891.aspx
I found out it is quite interesting on one of my custom entity, let’s call it “cust_selectionmatrix”. I tried to build the query using the tool, but I won’t generate the query as expected. Then I tried to look at Microsoft examples around the Web API query. Most of them are appending “s” against the entity name. E.g: for account: /api/data/v8.0/accounts and for contact: /api/data/v8.0/contacts.
So my first trial is just adding s at the end of my custom entity: /api/data/v8.0/cust_selectionmatrixs. However, I’ve got a weird error:
"Resource not found for the segment 'cust_selectionmatrixs'."
Then after I tried to find the list of entity for Web API using <CRM Server URL>/api/data/v8.0/. I found out that my entity is named: “cust_selectionmatrixes” in the Web API. I reckon this is how CRM is implementing “English”. So, if your entity ends with: ‑s, ‑sh, ‑ch, ‑x, or ‑z. Just append ‘es‘ to your entity name to work with the Web API.
Then.. There was an awkward moment when I have an entity named “cust_settings” and it is translated as “cust_settingses“…