diff --git a/include/mbedtls/chacha20.h b/include/mbedtls/chacha20.h
index 1c6cde0..2ae5e6e 100644
--- a/include/mbedtls/chacha20.h
+++ b/include/mbedtls/chacha20.h
@@ -88,9 +88,10 @@
 void mbedtls_chacha20_init( mbedtls_chacha20_context *ctx );
 
 /**
- * \brief           This function releases and clears the specified ChaCha20 context.
+ * \brief           This function releases and clears the specified
+ *                  ChaCha20 context.
  *
- * \param ctx       The ChaCha20 context to clear. May be \c NULL,
+ * \param ctx       The ChaCha20 context to clear. This may be \c NULL,
  *                  in which case this function is a no-op. If it is not
  *                  \c NULL, it must point to an initialized context.
  *
@@ -107,7 +108,8 @@
  *
  * \param ctx       The ChaCha20 context to which the key should be bound.
  *                  It must be initialized.
- * \param key       The encryption/decryption key. Must be 32 bytes in length.
+ * \param key       The encryption/decryption key. This must be \c 32 Bytes
+ *                  in length.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or key is NULL.
@@ -127,8 +129,8 @@
  *
  * \param ctx       The ChaCha20 context to which the nonce should be bound.
  *                  It must be initialized and bound to a key.
- * \param nonce     The nonce. Must be 12 bytes in size.
- * \param counter   The initial counter value. This is usually 0.
+ * \param nonce     The nonce. This must be \c 12 Bytes in size.
+ * \param counter   The initial counter value. This is usually \c 0.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or nonce is
@@ -157,11 +159,11 @@
  *
  * \param ctx       The ChaCha20 context to use for encryption or decryption.
  *                  It must be initialized and bound to a key and nonce.
- * \param size      The length of the input data in bytes.
+ * \param size      The length of the input data in Bytes.
  * \param input     The buffer holding the input data.
  *                  This pointer can be \c NULL if `size == 0`.
  * \param output    The buffer holding the output data.
- *                  Must be able to hold \p size bytes.
+ *                  This must be able to hold \p size Bytes.
  *                  This pointer can be \c NULL if `size == 0`.
  *
  * \return          \c 0 on success.
@@ -186,14 +188,15 @@
  * \note            The \p input and \p output pointers must either be equal or
  *                  point to non-overlapping buffers.
  *
- * \param key       The encryption/decryption key. Must be 32 bytes in length.
- * \param nonce     The nonce. Must be 12 bytes in size.
- * \param counter   The initial counter value. This is usually 0.
- * \param size      The length of the input data in bytes.
+ * \param key       The encryption/decryption key.
+ *                  This must be \c 32 Bytes in length.
+ * \param nonce     The nonce. This must be \c 12 Bytes in size.
+ * \param counter   The initial counter value. This is usually \c 0.
+ * \param size      The length of the input data in Bytes.
  * \param input     The buffer holding the input data.
  *                  This pointer can be \c NULL if `size == 0`.
  * \param output    The buffer holding the output data.
- *                  Must be able to hold \p size bytes.
+ *                  This must be able to hold \p size Bytes.
  *                  This pointer can be \c NULL if `size == 0`.
  *
  * \return          \c 0 on success.
diff --git a/include/mbedtls/chachapoly.h b/include/mbedtls/chachapoly.h
index 80d20e5..49e615d 100644
--- a/include/mbedtls/chachapoly.h
+++ b/include/mbedtls/chachapoly.h
@@ -123,7 +123,7 @@
  * \brief           This function releases and clears the specified
  *                  ChaCha20-Poly1305 context.
  *
- * \param ctx       The ChachaPoly context to clear. May be \c NULL, in which
+ * \param ctx       The ChachaPoly context to clear. This may be \c NULL, in which
  *                  case this function is a no-op.
  */
 void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx );
@@ -133,8 +133,8 @@
  *                  symmetric encryption key.
  *
  * \param ctx       The ChaCha20-Poly1305 context to which the key should be
- *                  bound. Must be initialized.
- * \param key       The 256-bit (32 bytes) key.
+ *                  bound. This must be initialized.
+ * \param key       The \c 256 Bit (\c 32 Bytes) key.
  *
  * \return          \c 0 on success.
  * \return          A negative error code on failure.
@@ -157,8 +157,10 @@
  * \warning         Decryption with the piecewise API is discouraged, see the
  *                  warning on \c mbedtls_chachapoly_init().
  *
- * \param ctx       The ChaCha20-Poly1305 context. Must be initialized.
- * \param nonce     The nonce/IV to use for the message. Must be 12 bytes.
+ * \param ctx       The ChaCha20-Poly1305 context. This must be initialized
+ *                  and bound to a key.
+ * \param nonce     The nonce/IV to use for the message.
+ *                  This must be a redable buffer of length \c 12 Bytes.
  * \param mode      The operation to perform: #MBEDTLS_CHACHAPOLY_ENCRYPT or
  *                  #MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning).
  *
@@ -194,11 +196,12 @@
  * \warning         Decryption with the piecewise API is discouraged, see the
  *                  warning on \c mbedtls_chachapoly_init().
  *
- * \param ctx       The ChaCha20-Poly1305 context to use.
- * \param aad_len   The length (in bytes) of the AAD. The length has no
+ * \param ctx       The ChaCha20-Poly1305 context. This must be initialized
+ *                  and bound to a key.
+ * \param aad_len   The length in Bytes of the AAD. The length has no
  *                  restrictions.
  * \param aad       Buffer containing the AAD.
- *                  This pointer can be NULL if aad_len == 0.
+ *                  This pointer can be \c NULL if `aad_len == 0`.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA
@@ -228,12 +231,12 @@
  * \warning         Decryption with the piecewise API is discouraged, see the
  *                  warning on \c mbedtls_chachapoly_init().
  *
- * \param ctx       The ChaCha20-Poly1305 context to use. Must be initialized.
+ * \param ctx       The ChaCha20-Poly1305 context to use. This must be initialized.
  * \param len       The length (in bytes) of the data to encrypt or decrypt.
  * \param input     The buffer containing the data to encrypt or decrypt.
  *                  This pointer can be \c NULL if `len == 0`.
  * \param output    The buffer to where the encrypted or decrypted data is
- *                  written. Must be able to hold \p len bytes.
+ *                  written. This must be able to hold \p len bytes.
  *                  This pointer can be \c NULL if `len == 0`.
  *
  * \return          \c 0 on success.
@@ -251,7 +254,7 @@
  * \brief           This function finished the ChaCha20-Poly1305 operation and
  *                  generates the MAC (authentication tag).
  *
- * \param ctx       The ChaCha20-Poly1305 context to use. Must be initialized.
+ * \param ctx       The ChaCha20-Poly1305 context to use. This must be initialized.
  * \param mac       The buffer to where the 128-bit (16 bytes) MAC is written.
  *
  * \warning         Decryption with the piecewise API is discouraged, see the
@@ -279,17 +282,18 @@
  *                  and key.
  *
  * \param ctx       The ChaCha20-Poly1305 context to use (holds the key).
- *                  Must be initialized.
+ *                  This must be initialized.
  * \param length    The length (in bytes) of the data to encrypt or decrypt.
  * \param nonce     The 96-bit (12 bytes) nonce/IV to use.
- * \param aad       The buffer containing the additional authenticated data (AAD).
- *                  This pointer can be \c NULL if `aad_len == 0`.
+ * \param aad       The buffer containing the additional authenticated
+ *                  data (AAD). This pointer can be \c NULL if `aad_len == 0`.
  * \param aad_len   The length (in bytes) of the AAD data to process.
  * \param input     The buffer containing the data to encrypt or decrypt.
  *                  This pointer can be \c NULL if `ilen == 0`.
- * \param output    The buffer to where the encrypted or decrypted data is written.
- *                  This pointer can be \c NULL if `ilen == 0`.
- * \param tag       The buffer to where the computed 128-bit (16 bytes) MAC is written.
+ * \param output    The buffer to where the encrypted or decrypted data
+ *                  is written. This pointer can be \c NULL if `ilen == 0`.
+ * \param tag       The buffer to where the computed 128-bit (16 bytes) MAC
+ *                  is written. This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          A negative error code on failure.
@@ -311,16 +315,17 @@
  *                  \c mbedtls_chachapoly_setkey().
  *
  * \param ctx       The ChaCha20-Poly1305 context to use (holds the key).
- * \param length    The length (in bytes) of the data to decrypt.
- * \param nonce     The 96-bit (12 bytes) nonce/IV to use.
+ * \param length    The length (in Bytes) of the data to decrypt.
+ * \param nonce     The \c 96 Bit (\c 12 bytes) nonce/IV to use.
  * \param aad       The buffer containing the additional authenticated data (AAD).
- *                  This pointer can be NULL if aad_len == 0.
+ *                  This pointer can be \c NULL if `aad_len == 0`.
  * \param aad_len   The length (in bytes) of the AAD data to process.
  * \param tag       The buffer holding the authentication tag.
+ *                  This must be a readable buffer of length \c 16 Bytes.
  * \param input     The buffer containing the data to decrypt.
- *                  This pointer can be NULL if ilen == 0.
+ *                  This pointer can be \c NULL if `ilen == 0`.
  * \param output    The buffer to where the decrypted data is written.
- *                  This pointer can be NULL if ilen == 0.
+ *                  This pointer can be \c NULL if `ilen == 0`.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED
diff --git a/include/mbedtls/poly1305.h b/include/mbedtls/poly1305.h
index 617958e..05866a2 100644
--- a/include/mbedtls/poly1305.h
+++ b/include/mbedtls/poly1305.h
@@ -84,15 +84,18 @@
  *                  \c mbedtls_poly1305_finish(), then finally
  *                  \c mbedtls_poly1305_free().
  *
- * \param ctx       The Poly1305 context to initialize. Must not be \c NULL.
+ * \param ctx       The Poly1305 context to initialize. This must
+ *                  not be \c NULL.
  */
 void mbedtls_poly1305_init( mbedtls_poly1305_context *ctx );
 
 /**
- * \brief           This function releases and clears the specified Poly1305 context.
+ * \brief           This function releases and clears the specified
+ *                  Poly1305 context.
  *
- * \param ctx       The Poly1305 context to clear. May be \c NULL, in which
- *                  case this function is a no-op.
+ * \param ctx       The Poly1305 context to clear. This may be \c NULL, in which
+ *                  case this function is a no-op. If it is not \c NULL, it must
+ *                  point to an initialized Poly1305 context.
  */
 void mbedtls_poly1305_free( mbedtls_poly1305_context *ctx );
 
@@ -103,8 +106,8 @@
  *                  invocation of Poly1305.
  *
  * \param ctx       The Poly1305 context to which the key should be bound.
- *                  Must be initialized.
- * \param key       The buffer containing the 32-byte (256-bit) key.
+ *                  This must be initialized.
+ * \param key       The buffer containing the \c 32 Byte (\c 256 Bit) key.
  *
  * \return          \c 0 on success.
  * \return          A negative error code on failure.
@@ -121,8 +124,8 @@
  *                  It can be called repeatedly to process a stream of data.
  *
  * \param ctx       The Poly1305 context to use for the Poly1305 operation.
- *                  Must be initialized.
- * \param ilen      The length of the input data (in bytes).
+ *                  This must be initialized and bound to a key.
+ * \param ilen      The length of the input data in Bytes.
  *                  Any value is accepted.
  * \param input     The buffer holding the input data.
  *                  This pointer can be \c NULL if `ilen == 0`.
@@ -139,9 +142,9 @@
  *                  Authentication Code (MAC).
  *
  * \param ctx       The Poly1305 context to use for the Poly1305 operation.
- *                  Must be initialized.
- * \param mac       The buffer to where the MAC is written. Must be big enough
- *                  to hold the 16-byte MAC.
+ *                  This must be initialized and bound to a key.
+ * \param mac       The buffer to where the MAC is written. This must
+ *                  be a writable buffer of length \c 16 Bytes.
  *
  * \return          \c 0 on success.
  * \return          A negative error code on failure.
@@ -156,13 +159,13 @@
  * \warning         The key must be unique and unpredictable for each
  *                  invocation of Poly1305.
  *
- * \param key       The buffer containing the 32-byte (256-bit) key.
- * \param ilen      The length of the input data (in bytes).
+ * \param key       The buffer containing the \c 32 Byte (\c 256 Bit) key.
+ * \param ilen      The length of the input data in Bytes.
  *                  Any value is accepted.
  * \param input     The buffer holding the input data.
  *                  This pointer can be \c NULL if `ilen == 0`.
- * \param mac       The buffer to where the MAC is written. Must be big enough
- *                  to hold the 16-byte MAC.
+ * \param mac       The buffer to where the MAC is written. This must be
+ *                  a writable buffer of length \c 16 Bytes.
  *
  * \return          \c 0 on success.
  * \return          A negative error code on failure.