diff --git a/common/collections.ts b/common/collections.ts
index e2043b2..e197cc6 100644
--- a/common/collections.ts
+++ b/common/collections.ts
@@ -1,4 +1,4 @@
-import { BigInt, BigDecimal } from './numbers'
+import { BigInt, BigDecimal, Address } from './numbers'
 import { Value } from './value'
 import { typeConversion } from './conversion'
 
@@ -67,7 +67,9 @@ export class ByteArray extends Uint8Array {
   }
 
   /**
-   * Input length must be even.
+   * Convert the string `hex` which must consist of an even number of
+   * hexadecimal digits to a `ByteArray`. The string `hex` can optionally
+   * start with '0x'
    */
   static fromHexString(hex: string): ByteArray {
     assert(hex.length % 2 == 0, 'input ' + hex + ' has odd length')
@@ -165,6 +167,21 @@ export class ByteArray extends Uint8Array {
     return x
   }
 
+  /** Create a new `ByteArray` that consist of `this` directly followed by
+   * the bytes from `other` */
+  concat(other: ByteArray): ByteArray {
+    let newArray = new ByteArray(this.length + other.length)
+    newArray.set(this, 0)
+    newArray.set(other, this.length)
+    return newArray
+  }
+
+  /** Create a new `ByteArray` that consists of `this` directly followed by
+   * the representation of `other` as bytes */
+  concatI32(other: i32): ByteArray {
+    return this.concat(ByteArray.fromI32(other))
+  }
+
   /**
    * Interprets the byte array as a little-endian I64.
    * Throws in case of overflow.
@@ -268,13 +285,34 @@ export class Bytes extends ByteArray {
     return changetype<Bytes>(uint8Array)
   }
 
+  /**
+   * Convert the string `hex` which must consist of an even number of
+   * hexadecimal digits to a `ByteArray`. The string `hex` can optionally
+   * start with '0x'
+   */
+  static fromHexString(str: string): Bytes {
+    return changetype<Bytes>(ByteArray.fromHexString(str))
+  }
+
   static fromUTF8(str: string): Bytes {
     return Bytes.fromByteArray(ByteArray.fromUTF8(str))
   }
 
+  static fromI32(i: i32): Bytes {
+    return changetype<Bytes>(ByteArray.fromI32(i))
+  }
+
   static empty(): Bytes {
     return changetype<Bytes>(ByteArray.empty())
   }
+
+  concat(other: Bytes): Bytes {
+    return changetype<Bytes>(super.concat(other))
+  }
+
+  concatI32(other: i32): Bytes {
+    return changetype<Bytes>(super.concat(ByteArray.fromI32(other)))
+  }
 }
 
 /**
diff --git a/common/numbers.ts b/common/numbers.ts
index f53c8eb..48ae2af 100644
--- a/common/numbers.ts
+++ b/common/numbers.ts
@@ -35,6 +35,17 @@ export class Address extends Bytes {
     return changetype<Address>(typeConversion.stringToH160(s))
   }
 
+  /** Convert `Bytes` that must be exactly 20 bytes long to an address.
+   * Passing in a value with fewer or more bytes will result in an error */
+  static fromBytes(b: Bytes): Address {
+    if (b.length != 20) {
+      throw new Error(
+        `Bytes of length ${b.length} can not be converted to 20 byte addresses`,
+      )
+    }
+    return changetype<Address>(b)
+  }
+
   static zero(): Address {
     let self = new ByteArray(20)
 
diff --git a/common/value.ts b/common/value.ts
index e229198..f2f5ec8 100644
--- a/common/value.ts
+++ b/common/value.ts
@@ -16,6 +16,17 @@ export enum ValueKind {
   BIGINT = 7,
 }
 
+const VALUE_KIND_NAMES = [
+  'String',
+  'Int',
+  'BigDecimal',
+  'bool',
+  'Array',
+  'null',
+  'Bytes',
+  'BigInt',
+]
+
 /**
  * Pointer type for Value data.
  *
@@ -129,6 +140,42 @@ export class Value {
     return output
   }
 
+  /** Return a string that indicates the kind of value `this` contains for
+   * logging and error messages */
+  displayKind(): string {
+    if (this.kind >= VALUE_KIND_NAMES.length) {
+      return `Unknown (${this.kind})`
+    } else {
+      return VALUE_KIND_NAMES[this.kind]
+    }
+  }
+
+  /** Return a string representation of the value of `this` for logging and
+   * error messages */
+  displayData(): string {
+    switch (this.kind) {
+      case ValueKind.STRING:
+        return this.toString()
+      case ValueKind.INT:
+        return this.toI32().toString()
+      case ValueKind.BIGDECIMAL:
+        return this.toBigDecimal().toString()
+      case ValueKind.BOOL:
+        return this.toBoolean().toString()
+      case ValueKind.ARRAY:
+        let arr = this.toArray()
+        return '[' + arr.map<string>((elt) => elt.displayData()).join(', ') + ']'
+      case ValueKind.NULL:
+        return 'null'
+      case ValueKind.BYTES:
+        return this.toBytes().toHexString()
+      case ValueKind.BIGINT:
+        return this.toBigInt().toString()
+      default:
+        return `Unknown data (kind = ${this.kind})`
+    }
+  }
+
   static fromBooleanArray(input: Array<boolean>): Value {
     let output = new Array<Value>(input.length)
     for (let i: i32 = 0; i < input.length; i++) {
diff --git a/package.json b/package.json
index aaf742d..74b4597 100644
--- a/package.json
+++ b/package.json
@@ -13,6 +13,7 @@
   },
   "scripts": {
     "lint": "prettier -c **/*.{js,ts}",
+    "format": "prettier --write -c **/*.{js,ts}",
     "build": "asc --explicitStart --exportRuntime --runtime stub index.ts helper-functions.ts --lib graph-ts -b index.wasm",
     "test": "node test/test.js"
   }