diff --git a/packages/api-format/package.json b/packages/api-format/package.json
index d268506956c4..c066bbce882e 100644
--- a/packages/api-format/package.json
+++ b/packages/api-format/package.json
@@ -33,6 +33,7 @@
     "@polkadot/api-jsonrpc": "^0.6.4"
   },
   "dependencies": {
+    "@polkadot/primitives-json": "^0.1.5",
     "@polkadot/util": "^0.6.7",
     "babel-runtime": "^6.26.0"
   }
diff --git a/packages/api-format/src/input.js b/packages/api-format/src/input.js
new file mode 100644
index 000000000000..f991915d25cb
--- /dev/null
+++ b/packages/api-format/src/input.js
@@ -0,0 +1,26 @@
+// ISC, Copyright 2017 Jaco Greeff
+// @flow
+
+import type { FormatInputType, InterfaceInputType } from '@polkadot/api-jsonrpc/types';
+import type { FormatterFunction } from './types';
+
+const accountIdToJson = require('@polkadot/primitives-json/accountId/toJson');
+const h256ToJson = require('@polkadot/primitives-json/h256/toJson');
+const hashToJson = require('@polkadot/primitives-json/hash/toJson');
+
+const formatNoop = require('./noop');
+const util = require('./util');
+
+const formatters: { [FormatInputType]: FormatterFunction } = {
+  'Address': accountIdToJson,
+  'CallData': hashToJson,
+  'H256': h256ToJson,
+  'HeaderHash': h256ToJson,
+  'String': formatNoop
+};
+
+module.exports = function formatInputs (inputs: Array<InterfaceInputType>, values: Array<any>): Array<any> {
+  const types = inputs.map(({ type }) => type);
+
+  return util.formatArray(formatters, types, values);
+};
diff --git a/packages/api-format/src/input/index.spec.js b/packages/api-format/src/input.spec.js
similarity index 82%
rename from packages/api-format/src/input/index.spec.js
rename to packages/api-format/src/input.spec.js
index e7af4f1d4709..902f112f6701 100644
--- a/packages/api-format/src/input/index.spec.js
+++ b/packages/api-format/src/input.spec.js
@@ -1,12 +1,12 @@
 // ISC, Copyright 2017 Jaco Greeff
 
-const format = require('./index');
+const { formatInputs } = require('./index');
 
-describe('input', () => {
+describe('formatInputs', () => {
   describe('format', () => {
     it('formats each value in an array', () => {
       expect(
-        format(
+        formatInputs(
           [
             { name: 'foo', type: 'Address' },
             { name: 'bar', type: 'H256' }
diff --git a/packages/api-format/src/input/address.js b/packages/api-format/src/input/address.js
deleted file mode 100644
index 9809ffc21266..000000000000
--- a/packages/api-format/src/input/address.js
+++ /dev/null
@@ -1,10 +0,0 @@
-// ISC, Copyright 2017 Jaco Greeff
-// @flow
-
-const { formatH160 } = require('./hex');
-
-// TODO: Currently the format assumes 160-bit values (like Ethereum)
-// this will probably change along the way as things get firmed up
-module.exports = function format (value: ?string): string {
-  return formatH160(value);
-};
diff --git a/packages/api-format/src/input/address.spec.js b/packages/api-format/src/input/address.spec.js
deleted file mode 100644
index 700459777b6f..000000000000
--- a/packages/api-format/src/input/address.spec.js
+++ /dev/null
@@ -1,13 +0,0 @@
-// ISC, Copyright 2017 Jaco Greeff
-
-const format = require('./address');
-
-describe('input/address', () => {
-  describe('format', () => {
-    it('pads to H160 value', () => {
-      expect(
-        format('0x1234567890')
-      ).toEqual('0x0000000000000000000000000000001234567890');
-    });
-  });
-});
diff --git a/packages/api-format/src/input/hex.js b/packages/api-format/src/input/hex.js
deleted file mode 100644
index 4d72e946b8a1..000000000000
--- a/packages/api-format/src/input/hex.js
+++ /dev/null
@@ -1,33 +0,0 @@
-// ISC, Copyright 2017 Jaco Greeff
-// @flow
-
-const { hexAddPrefix, hexHasPrefix, hexStripPrefix } = require('@polkadot/util/hex');
-
-const H64_ZERO: string = '00000000000000000000000000000000';
-const H128_ZERO: string = `${H64_ZERO}${H64_ZERO}`;
-const H256_ZERO: string = `${H128_ZERO}${H128_ZERO}`;
-// const H512_ZERO: string = `${H256_ZERO}${H256_ZERO}`;
-
-function leftHexPad (value: ?string, bitLength: number): string {
-  const length = 2 * bitLength / 8;
-
-  if (hexHasPrefix(value)) {
-    value = hexStripPrefix(value);
-  }
-
-  return hexAddPrefix(`${H256_ZERO}${value || ''}`.slice(-length));
-}
-
-function formatH160 (value: ?string): string {
-  return leftHexPad(value, 160);
-}
-
-function formatH256 (value: ?string): string {
-  return leftHexPad(value, 256);
-}
-
-module.exports = {
-  leftHexPad,
-  formatH160,
-  formatH256
-};
diff --git a/packages/api-format/src/input/hex.spec.js b/packages/api-format/src/input/hex.spec.js
deleted file mode 100644
index cae7cc973580..000000000000
--- a/packages/api-format/src/input/hex.spec.js
+++ /dev/null
@@ -1,53 +0,0 @@
-// ISC, Copyright 2017 Jaco Greeff
-
-const { leftHexPad, formatH160, formatH256 } = require('./hex');
-
-describe('input/hex', () => {
-  describe('leftHexPad', () => {
-    it('padds to the required length', () => {
-      expect(
-        leftHexPad('0x123', 16)
-      ).toEqual('0x0123');
-    });
-
-    it('padds to the required length (no prefix)', () => {
-      expect(
-        leftHexPad('123', 16)
-      ).toEqual('0x0123');
-    });
-
-    it('pads null values correctly', () => {
-      expect(
-        leftHexPad(null, 16)
-      ).toEqual('0x0000');
-    });
-  });
-
-  describe('formatH160', () => {
-    it('pads to 40 bytes', () => {
-      expect(
-        formatH160('0x1234567890')
-      ).toEqual('0x0000000000000000000000000000001234567890');
-    });
-
-    it('pads null values correctly', () => {
-      expect(
-        formatH160(null)
-      ).toMatch(/^0x(00){20,}$/);
-    });
-  });
-
-  describe('formatH256', () => {
-    it('pads to 64 bytes', () => {
-      expect(
-        formatH256('0x1234567890')
-      ).toEqual('0x0000000000000000000000000000000000000000000000000000001234567890');
-    });
-
-    it('pads null values correctly', () => {
-      expect(
-        formatH256(null)
-      ).toMatch(/^0x(00){32,}$/);
-    });
-  });
-});
diff --git a/packages/api-format/src/input/index.js b/packages/api-format/src/input/index.js
deleted file mode 100644
index 8fcb6f52c11d..000000000000
--- a/packages/api-format/src/input/index.js
+++ /dev/null
@@ -1,24 +0,0 @@
-// ISC, Copyright 2017 Jaco Greeff
-// @flow
-
-import type { FormatInputType, InterfaceInputType } from '@polkadot/api-jsonrpc/types';
-import type { FormatterFunction } from '../types';
-
-const formatAddress = require('./address');
-const { formatH256 } = require('./hex');
-const formatNoop = require('../noop');
-const util = require('../util');
-
-const formatters: { [FormatInputType]: FormatterFunction } = {
-  'Address': formatAddress,
-  'CallData': formatNoop,
-  'H256': formatH256,
-  'HeaderHash': formatH256,
-  'String': formatNoop
-};
-
-module.exports = function format (inputs: Array<InterfaceInputType>, values: Array<any>): Array<any> {
-  const types = inputs.map(({ type }) => type);
-
-  return util.formatArray(formatters, types, values);
-};
diff --git a/packages/api-format/src/output/index.js b/packages/api-format/src/output.js
similarity index 50%
rename from packages/api-format/src/output/index.js
rename to packages/api-format/src/output.js
index a0322c7a6e1d..4c9d3cf45df2 100644
--- a/packages/api-format/src/output/index.js
+++ b/packages/api-format/src/output.js
@@ -2,17 +2,19 @@
 // @flow
 
 import type { FormatOutputType, InterfaceOutputType } from '@polkadot/api-jsonrpc/types';
-import type { FormatterFunction } from '../types';
+import type { FormatterFunction } from './types';
 
-const formatNoop = require('../noop');
-const util = require('../util');
+const headerFromJson = require('@polkadot/primitives-json/header/fromJson');
+
+const formatNoop = require('./noop');
+const util = require('./util');
 
 const formatters: { [FormatOutputType]: FormatterFunction } = {
-  'Header': formatNoop,
+  'Header': headerFromJson,
   'OutData': formatNoop,
   'StorageData': formatNoop
 };
 
-module.exports = function format (output: InterfaceOutputType, value: any): any {
+module.exports = function formatOutput (output: InterfaceOutputType, value: any): any {
   return util.format(formatters, output.type, value);
 };
diff --git a/packages/api-format/src/output.spec.js b/packages/api-format/src/output.spec.js
new file mode 100644
index 000000000000..152318eae3aa
--- /dev/null
+++ b/packages/api-format/src/output.spec.js
@@ -0,0 +1,40 @@
+// ISC, Copyright 2017 Jaco Greeff
+
+const BN = require('bn.js');
+
+const { formatOutput } = require('./index');
+
+describe('formatOutput', () => {
+  describe('format', () => {
+    it('formats the value', () => {
+      expect(
+        JSON.stringify(
+          formatOutput({ type: 'Header' }, {
+            parentHash: '0x1234',
+            number: '0x1234',
+            stateRoot: '0x5678',
+            transactionRoot: '0xabcd',
+            digest: {
+              parachainActivityBitfield: '0x1234',
+              logs: ['0x5678', '0x789a']
+            }
+          })
+        )
+      ).toEqual(
+        JSON.stringify({
+          parentHash: '0x1234',
+          number: new BN(0x1234),
+          stateRoot: '0x5678',
+          transactionRoot: '0xabcd',
+          digest: {
+            parachainActivityBitfield: Buffer.from([0x12, 0x34]),
+            logs: [
+              Buffer.from([0x56, 0x78]),
+              Buffer.from([0x78, 0x9a])
+            ]
+          }
+        })
+      );
+    });
+  });
+});
diff --git a/packages/api-format/src/output/index.spec.js b/packages/api-format/src/output/index.spec.js
deleted file mode 100644
index e73c1fa7e925..000000000000
--- a/packages/api-format/src/output/index.spec.js
+++ /dev/null
@@ -1,13 +0,0 @@
-// ISC, Copyright 2017 Jaco Greeff
-
-const format = require('./index');
-
-describe('output', () => {
-  describe('format', () => {
-    it('formats the value', () => {
-      expect(
-        format('Header', 'test')
-      ).toEqual('test');
-    });
-  });
-});
diff --git a/packages/api-format/src/util.js b/packages/api-format/src/util.js
index 0aaea0e20694..218b2a2a8b82 100644
--- a/packages/api-format/src/util.js
+++ b/packages/api-format/src/util.js
@@ -45,9 +45,7 @@ function format (formatters: { [any]: FormatterFunction }, type: string, value:
 
 function formatArray (formatters: { [any]: FormatterFunction }, types: Array<string>, values: Array<any>): Array<any> {
   return types.map((type, index) => {
-    const value = values[index];
-
-    return format(formatters, type, value);
+    return format(formatters, type, values[index]);
   });
 }
 
diff --git a/yarn.lock b/yarn.lock
index f2c10badce29..3476703c2ccf 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -91,6 +91,17 @@
     stylelint "^8.2.0"
     stylelint-config-standard "^18.0.0"
 
+"@polkadot/primitives-json@^0.1.5":
+  version "0.1.5"
+  resolved "https://registry.yarnpkg.com/@polkadot/primitives-json/-/primitives-json-0.1.5.tgz#bd3f1dc2532190ebf78ba9d89f64b518d105eae8"
+  dependencies:
+    "@polkadot/primitives" "^0.1.5"
+    "@polkadot/util" "^0.6.8"
+
+"@polkadot/primitives@^0.1.5":
+  version "0.1.5"
+  resolved "https://registry.yarnpkg.com/@polkadot/primitives/-/primitives-0.1.5.tgz#6eb2fbccb06bda8bd774d205528d9b3a1d3e0b21"
+
 "@polkadot/util@^0.6.7":
   version "0.6.7"
   resolved "https://registry.yarnpkg.com/@polkadot/util/-/util-0.6.7.tgz#eb9a6bd3717b69c962f6fb70830ebc60380c333f"
@@ -99,6 +110,14 @@
     bn.js "^4.11.8"
     keccak "^1.3.0"
 
+"@polkadot/util@^0.6.8":
+  version "0.6.10"
+  resolved "https://registry.yarnpkg.com/@polkadot/util/-/util-0.6.10.tgz#09417e607ec64a404ae63fa64f8f008d91c79856"
+  dependencies:
+    babel-runtime "^6.26.0"
+    bn.js "^4.11.8"
+    keccak "^1.3.0"
+
 JSONStream@^1.0.4:
   version "1.3.1"
   resolved "https://registry.yarnpkg.com/JSONStream/-/JSONStream-1.3.1.tgz#707f761e01dae9e16f1bcf93703b78c70966579a"