diff --git a/pkg/core/block/block.go b/pkg/core/block/block.go
index aae9c30c1..9b246a4d3 100644
--- a/pkg/core/block/block.go
+++ b/pkg/core/block/block.go
@@ -35,7 +35,9 @@ type Block struct {
 	// Transaction list.
 	Transactions []*transaction.Transaction
 
-	// True if this block is created from trimmed data.
+	// True if this block is created from trimmed data (with a proper
+	// header and hashes-only transactions). Not a part of a real
+	// block and is used only by internal packages.
 	Trimmed bool
 }
 
diff --git a/pkg/core/block/header.go b/pkg/core/block/header.go
index b56e1cbba..2edd763dc 100644
--- a/pkg/core/block/header.go
+++ b/pkg/core/block/header.go
@@ -16,9 +16,10 @@ import (
 // VersionInitial is the default Neo block version.
 const VersionInitial uint32 = 0
 
-// Header holds the base info of a block.
+// Header holds the base info of a block. Fields follow the P2P format of the
+// N3 block header unless noted specifically.
 type Header struct {
-	// Version of the block.
+	// Version of the block, currently only 0.
 	Version uint32
 
 	// hash of the previous block.
@@ -42,12 +43,18 @@ type Header struct {
 	// Contract address of the next miner
 	NextConsensus util.Uint160
 
-	// Script used to validate the block
+	// Witness scripts used for block validation. These scripts
+	// are not a part of a hashable field set.
 	Script transaction.Witness
 
 	// StateRootEnabled specifies if the header contains state root.
+	// It's NeoGo-specific, and is not a part of a standard Neo N3 header,
+	// it's also never serialized into P2P payload. When it's false
+	// PrevStateRoot is always zero, when true it works as intended.
 	StateRootEnabled bool
-	// PrevStateRoot is the state root of the previous block.
+	// PrevStateRoot is the state root of the previous block. This field
+	// is relevant only if StateRootEnabled is true which is a
+	// NeoGo-specific extension of the protocol.
 	PrevStateRoot util.Uint256
 	// PrimaryIndex is the index of the primary consensus node for this block.
 	PrimaryIndex byte
@@ -73,7 +80,10 @@ type baseAux struct {
 	Witnesses     []transaction.Witness `json:"witnesses"`
 }
 
-// Hash returns the hash of the block.
+// Hash returns the hash of the block. Notice that it is cached internally,
+// so no matter how you change the [Header] after the first invocation of this
+// method it won't change. To get an updated hash in case you're changing
+// the [Header] please encode/decode it.
 func (b *Header) Hash() util.Uint256 {
 	if b.hash.Equals(util.Uint256{}) {
 		b.createHash()
@@ -81,7 +91,8 @@ func (b *Header) Hash() util.Uint256 {
 	return b.hash
 }
 
-// DecodeBinary implements the Serializable interface.
+// DecodeBinary implements the [io.Serializable] interface. Notice that it
+// also automatically updates the internal hash cache, see [Header.Hash].
 func (b *Header) DecodeBinary(br *io.BinReader) {
 	b.decodeHashableFields(br)
 	witnessCount := br.ReadVarUint()
diff --git a/pkg/core/transaction/transaction.go b/pkg/core/transaction/transaction.go
index e34344327..61d605270 100644
--- a/pkg/core/transaction/transaction.go
+++ b/pkg/core/transaction/transaction.go
@@ -34,13 +34,13 @@ var ErrInvalidWitnessNum = errors.New("number of signers doesn't match witnesses
 
 // Transaction is a process recorded in the Neo blockchain.
 type Transaction struct {
-	// The trading version which is currently 0.
+	// Version of the binary transaction format, currently only 0.
 	Version uint8
 
 	// Random number to avoid hash collision.
 	Nonce uint32
 
-	// Fee to be burned.
+	// Fee to be used for script execution and burned.
 	SystemFee int64
 
 	// Fee to be distributed to consensus nodes.
@@ -75,7 +75,7 @@ type Transaction struct {
 	hashed bool
 
 	// Trimmed indicates this is a transaction from trimmed
-	// data.
+	// data, meaning it doesn't have anything but hash.
 	Trimmed bool
 }
 
@@ -103,7 +103,11 @@ func New(script []byte, gas int64) *Transaction {
 	}
 }
 
-// Hash returns the hash of the transaction.
+// Hash returns the hash of the transaction which is based on serialized
+// representation of its fields. Notice that this hash is cached internally
+// in [Transaction] for efficiency, so once you call this method it will not
+// change even if you change any structure fields. If you need to update the
+// hash use encoding/decoding or [Transaction.Copy].
 func (t *Transaction) Hash() util.Uint256 {
 	if !t.hashed {
 		if t.createHash() != nil {
@@ -208,7 +212,9 @@ func (t *Transaction) decodeBinaryNoSize(br *io.BinReader, buf []byte) {
 	}
 }
 
-// DecodeBinary implements the Serializable interface.
+// DecodeBinary implements the [io.Serializable] interface. It also
+// computes and caches transaction hash and size (see [Transaction.Hash] and
+// [Transaction.Size]).
 func (t *Transaction) DecodeBinary(br *io.BinReader) {
 	t.decodeBinaryNoSize(br, nil)
 
@@ -294,7 +300,9 @@ func (t *Transaction) Bytes() []byte {
 	return buf.Bytes()
 }
 
-// NewTransactionFromBytes decodes byte array into *Transaction.
+// NewTransactionFromBytes decodes byte array into [*Transaction]. It also
+// computes and caches transaction hash and size (see [Transaction.Hash] and
+// [Transaction.Size]).
 func NewTransactionFromBytes(b []byte) (*Transaction, error) {
 	tx := &Transaction{}
 	r := io.NewBinReaderFromBuf(b)
@@ -315,7 +323,10 @@ func (t *Transaction) FeePerByte() int64 {
 	return t.NetworkFee / int64(t.Size())
 }
 
-// Size returns size of the serialized transaction.
+// Size returns size of the serialized transaction. This value is cached
+// in the [Transaction], so once you obtain it no changes to fields will be
+// reflected in value returned from this method, use encoding/decoding or
+// [Transaction.Copy] if needed.
 func (t *Transaction) Size() int {
 	if t.size == 0 {
 		t.size = io.GetVarSize(t)
@@ -469,8 +480,10 @@ func (t *Transaction) ToStackItem() stackitem.Item {
 	})
 }
 
-// Copy creates a deep copy of the Transaction, including all slice fields. Cached values like
-// 'hashed' and 'size' are reset to ensure the copy can be modified independently of the original.
+// Copy creates a deep copy of the Transaction, including all slice fields.
+// Cached values like hash and size are reset to ensure the copy can be
+// modified independently of the original (see [Transaction.Hash] and
+// [Transaction.Size]).
 func (t *Transaction) Copy() *Transaction {
 	if t == nil {
 		return nil