diff --git a/README.md b/README.md
index dbd6501..c29017e 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,15 @@
+## Requiriements
+
+A recent version of [Crystal](https://crystal-lang.org/install) and [Rust](https://www.rust-lang.org/tools/install).
+
 ## Building
 
-Instruction for building crystal project and rust library
+Instruction for building crystal project and the `verke_crypto` rust library it depends on.
 
 ```sh
-$ (cd verkle_crypto; cargo build) 
-$ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH CRYSTAL_OPTS="--link-flags=-Wl,-ld_classic" GC_DONT_GC=1 crystal build src/main.cr -o pampero
+$ (cd verkle_crypto; cargo build --release)
+$ shards install
+$ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH crystal build src/main.cr -o pampero
 ```
 
 ## Show block details
@@ -12,13 +17,13 @@ $ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH CRYSTAL_OPTS="--l
 Block at latest slot
 
 ```sh
-$ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH CRYSTAL_OPTS="--link-flags=-Wl,-ld_classic" GC_DONT_GC=1 crystal run src/dump_block.cr
+$ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH crystal run src/dump_block.cr
 ```
 
 Block at slot 831627
 
 ```sh
-$ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH CRYSTAL_OPTS="--link-flags=-Wl,-ld_classic" GC_DONT_GC=1 crystal run src/dump_block.cr  -- 831627
+$ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH crystal run src/dump_block.cr  -- 831627
 ```
 
 ## Unit tests
@@ -26,6 +31,6 @@ $ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH CRYSTAL_OPTS="--l
 To run all the tests
 
 ```sh
-$ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH CRYSTAL_OPTS="--link-flags=-Wl,-ld_classic" GC_DONT_GC=1 crystal spec
+$ LIBRARY_PATH=$(PWD)/verkle_crypto/target/debug:$LIBRARY_PATH crystal spec
 ```
 
diff --git a/src/config.cr b/src/config.cr
index 47bd089..db16cfc 100644
--- a/src/config.cr
+++ b/src/config.cr
@@ -1,10 +1,9 @@
 module Pampero
-
   class Config
     getter beacon_node : String
 
     def initialize
-      @beacon_node = ENV["BEACON_NODE"] || ""
+      @beacon_node = ENV["BEACON_NODE"]? || ""
     end
   end
 end
diff --git a/src/models/account.cr b/src/models/account.cr
index 9ebbb60..3a87fe2 100644
--- a/src/models/account.cr
+++ b/src/models/account.cr
@@ -1,5 +1,6 @@
 require "../common/types"
 require "../common/constants"
+require "json"
 
 module Pampero
   struct Account