Error: Unknown directive "@entity"

I'm using thegraph.com's schema convention e.g., [https://thegraph.com/docs/developer/create-subgraph-hosted#good-example](https://thegraph.com/docs/developer/create-subgraph-hosted#good-example). My schema looks like this:
```graphql
type Item @entity {
id: ID!
var1: BigInt!
var2: BigInt!
name: String!
}
```
I get this error when I run `npx graphql-markdown schema.graphql schema.md`:
```
Error: Unknown directive "@entity".
Unknown type "BigInt". Did you mean "Int"?
```

Can this tool accommodate or should I look elsewhere for a solution? Ty