update readme

Author: macalinao

README.md

@@ -6,7 +6,7 @@ Generates a crate for cross-program invocations to an Anchor program from a JSON
 
 In a new crate, write:
 
-```rust
+```skip
 anchor_gen::generate_cpi_crate!("../../examples/govern-cpi/idl.json");
 
 declare_id!("GjphYQcbP1m3FuDyCTUJf2mUMxKPE3j6feWU1rxvC7Ps");
@@ -16,4 +16,6 @@ This will generate a fully functional Rust CPI client for your IDL.
 
 More examples can be found in the [examples/](https://github.com/saber-hq/anchor-gen/tree/master/examples) directory.
 
+Note: This does not work on legacy IDLs. To migrate a legacy IDL, use `anchor idl convert idl.json`.
+
 License: Apache-2.0

crates/anchor-gen/README.md

@@ -0,0 +1,21 @@
+# anchor-gen
+
+Generates a crate for cross-program invocations to an Anchor program from a JSON IDL.
+
+## Usage
+
+In a new crate, write:
+
+```skip
+anchor_gen::generate_cpi_crate!("../../examples/govern-cpi/idl.json");
+
+declare_id!("GjphYQcbP1m3FuDyCTUJf2mUMxKPE3j6feWU1rxvC7Ps");
+```
+
+This will generate a fully functional Rust CPI client for your IDL.
+
+More examples can be found in the [examples/](https://github.com/saber-hq/anchor-gen/tree/master/examples) directory.
+
+Note: This does not work on legacy IDLs. To migrate a legacy IDL, use `anchor idl convert idl.json`.
+
+License: Apache-2.0

crates/anchor-gen/src/lib.rs

@@ -13,6 +13,8 @@
 //! This will generate a fully functional Rust CPI client for your IDL.
 //!
 //! More examples can be found in the [examples/](https://github.com/saber-hq/anchor-gen/tree/master/examples) directory.
+//!
+//! Note: This does not work on legacy IDLs. To migrate a legacy IDL, use `anchor idl convert idl.json`.
 
 pub use anchor_generate_cpi_crate::generate_cpi_crate;
 pub use anchor_generate_cpi_interface::generate_cpi_interface;

flake.nix

@@ -27,6 +27,7 @@
               rustup
               anchor
               cargo-expand
+              cargo-readme
             ];
           };
       }