diff --git a/docs/api.md b/docs/api.md
index c5a67dbf9e..3baf011b76 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -1,26 +1,33 @@
 #TREZOR OS API
 
+Syntax used below are valid Python function declarations with anotations defined in [PEP 3107](https://www.python.org/dev/peps/pep-3107/).
+
 ##trezor.crypto
 
 ###trezor.crypto.ed25519
 
-```
-def to_public(bytes[32] secret_key) => bytes[32] public_key
+``` python
+def to_public(secret_key: bytes[32]) -> bytes[32]: # public_key
 
-def sign(bytes message, bytes[32] secret_key, bytes[32] public_key = None) => bytes[64] signature
+def sign(message: bytes, secret_key: bytes[32], public_key: bytes[32] = None) -> bytes[64]: # signature
 
-def verify(bytes message, bytes[32] public_key, bytes[64] signature) => bool valid
+def verify(message: bytes, public_key: bytes[32], signature: bytes[64]) -> bool: # valid
 ```
 
 ###trezor.crypto.func
 
-```
-aes()
-base58()
-hmac()
-sha256()
-ripemd160()
-pbkdf2()
+``` python
+def aes():
+
+def base58():
+
+def hmac():
+
+def sha256():
+
+def ripemd160():
+
+def pbkdf2():
 ```
 
 ###trezor.crypto.hd
@@ -29,22 +36,22 @@ pbkdf2()
 
 ###trezor.crypto.nistp256
 
-```
-def to_public()
+``` python
+def to_public(secret_key: bytes[32]) -> bytes[33]: # public_key
 
-def sign()
+def sign(message: bytes, secret_key: bytes[32], public_key: bytes[33] = None) -> bytes[65]: # signature
 
-def verify()
+def verify(message: bytes, public_key: bytes[33], signature: bytes[65]) -> bool: # valid
 ```
 
 ###trezor.crypto.secp256k1
 
-```
-def to_public()
+``` python
+def to_public(secret_key: bytes[32]) -> bytes[33]: # public_key
 
-def sign()
+def sign(message: bytes, secret_key: bytes[32], public_key: bytes[33] = None) -> bytes[65]: # signature
 
-def verify()
+def verify(message: bytes, public_key: bytes[33], signature: bytes[65]) -> bool: # valid
 ```
 
 ##trezor.hw
@@ -53,9 +60,11 @@ def verify()
 
 ###trezor.hw.display
 
-##trezor.qrenc
+##trezor.utils
 
-```
+###trezor.utils.qrenc
+
+``` python
 enum QRLEVEL {
   L = 0,
   M = 1,
@@ -63,5 +72,5 @@ enum QRLEVEL {
   H = 3,
 }
 
-def encode(bytes source, qrlevel level = QRLEVEL.H) => bool[][] qrcode
+def encode(source: bytes, level: QRLEVEL = QRLEVEL.H) -> bool[][]: # qrcode
 ```