Documentation fixes

diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index f1ce746..24951a6 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -210,7 +210,7 @@
 void mbedtls_pk_init( mbedtls_pk_context *ctx );
 
 /**
- * \brief           Free a mbedtls_pk_context
+ * \brief           Free the components of a #mbedtls_pk_context.
  *
  * \param ctx       The context to clear. It must have been initialized.
  *                  If this is \c NULL, this function does nothing.