diff --git a/internal/telemetry/event/event.go b/internal/telemetry/event/event.go
index 6028fa6d2b..2b990c5c1e 100644
--- a/internal/telemetry/event/event.go
+++ b/internal/telemetry/event/event.go
@@ -72,7 +72,7 @@ func (ev Event) Format(f fmt.State, r rune) {
 		tag := ev.Tag(index)
 		// msg and err were both already printed above, so we skip them to avoid
 		// double printing
-		if !tag.Valid() || tag.Key == Msg || tag.Key == Err {
+		if !tag.Valid() || tag.Key() == Msg || tag.Key() == Err {
 			continue
 		}
 		fmt.Fprintf(f, "\n\t%v", tag)
@@ -90,14 +90,14 @@ func (ev Event) Tag(index int) Tag {
 	return ev.dynamic[index-len(ev.static)]
 }
 
-func (ev Event) Find(key interface{}) Tag {
+func (ev Event) Find(key Key) Tag {
 	for _, tag := range ev.static {
-		if tag.Key == key {
+		if tag.Key() == key {
 			return tag
 		}
 	}
 	for _, tag := range ev.dynamic {
-		if tag.Key == key {
+		if tag.Key() == key {
 			return tag
 		}
 	}
diff --git a/internal/telemetry/event/key.go b/internal/telemetry/event/key.go
index 97572c37f1..503ec50dda 100644
--- a/internal/telemetry/event/key.go
+++ b/internal/telemetry/event/key.go
@@ -17,7 +17,9 @@ var (
 	Err = NewErrorKey("error", "an error that occurred")
 )
 
-// Key is the interface shared by all key implementations.
+// Key is used as the identity of a Tag.
+// Keys are intended to be compared by pointer only, the name should be unique
+// for communicating with external systems, but it is not required or enforced.
 type Key interface {
 	// Name returns the key name.
 	Name() string
@@ -25,14 +27,6 @@ type Key interface {
 	Description() string
 }
 
-// key is used as the identity of a Tag.
-// Keys are intended to be compared by pointer only, the name should be unique
-// for communicating with external systems, but it is not required or enforced.
-type key struct {
-	name        string
-	description string
-}
-
 // ValueKey represents a key for untyped values.
 type ValueKey struct {
 	name        string
@@ -56,10 +50,10 @@ func (k *ValueKey) Get(tags TagMap) interface{} {
 }
 
 // From can be used to get a value from a Tag.
-func (k *ValueKey) From(t Tag) interface{} { return t.untyped }
+func (k *ValueKey) From(t Tag) interface{} { return t.UnpackValue() }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *ValueKey) Of(value interface{}) Tag { return Tag{Key: k, untyped: value} }
+func (k *ValueKey) Of(value interface{}) Tag { return TagOfValue(k, value) }
 
 // IntKey represents a key
 type IntKey struct {
@@ -76,7 +70,7 @@ func (k *IntKey) Name() string        { return k.name }
 func (k *IntKey) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *IntKey) Of(v int) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *IntKey) Of(v int) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *IntKey) Get(tags TagMap) int {
@@ -87,7 +81,7 @@ func (k *IntKey) Get(tags TagMap) int {
 }
 
 // From can be used to get a value from a Tag.
-func (k *IntKey) From(t Tag) int { return int(t.packed) }
+func (k *IntKey) From(t Tag) int { return int(t.Unpack64()) }
 
 // Int8Key represents a key
 type Int8Key struct {
@@ -104,7 +98,7 @@ func (k *Int8Key) Name() string        { return k.name }
 func (k *Int8Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *Int8Key) Of(v int8) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *Int8Key) Of(v int8) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *Int8Key) Get(tags TagMap) int8 {
@@ -115,7 +109,7 @@ func (k *Int8Key) Get(tags TagMap) int8 {
 }
 
 // From can be used to get a value from a Tag.
-func (k *Int8Key) From(t Tag) int8 { return int8(t.packed) }
+func (k *Int8Key) From(t Tag) int8 { return int8(t.Unpack64()) }
 
 // Int16Key represents a key
 type Int16Key struct {
@@ -132,7 +126,7 @@ func (k *Int16Key) Name() string        { return k.name }
 func (k *Int16Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *Int16Key) Of(v int16) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *Int16Key) Of(v int16) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *Int16Key) Get(tags TagMap) int16 {
@@ -143,7 +137,7 @@ func (k *Int16Key) Get(tags TagMap) int16 {
 }
 
 // From can be used to get a value from a Tag.
-func (k *Int16Key) From(t Tag) int16 { return int16(t.packed) }
+func (k *Int16Key) From(t Tag) int16 { return int16(t.Unpack64()) }
 
 // Int32Key represents a key
 type Int32Key struct {
@@ -160,7 +154,7 @@ func (k *Int32Key) Name() string        { return k.name }
 func (k *Int32Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *Int32Key) Of(v int32) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *Int32Key) Of(v int32) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *Int32Key) Get(tags TagMap) int32 {
@@ -171,7 +165,7 @@ func (k *Int32Key) Get(tags TagMap) int32 {
 }
 
 // From can be used to get a value from a Tag.
-func (k *Int32Key) From(t Tag) int32 { return int32(t.packed) }
+func (k *Int32Key) From(t Tag) int32 { return int32(t.Unpack64()) }
 
 // Int64Key represents a key
 type Int64Key struct {
@@ -188,7 +182,7 @@ func (k *Int64Key) Name() string        { return k.name }
 func (k *Int64Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *Int64Key) Of(v int64) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *Int64Key) Of(v int64) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *Int64Key) Get(tags TagMap) int64 {
@@ -199,7 +193,7 @@ func (k *Int64Key) Get(tags TagMap) int64 {
 }
 
 // From can be used to get a value from a Tag.
-func (k *Int64Key) From(t Tag) int64 { return int64(t.packed) }
+func (k *Int64Key) From(t Tag) int64 { return int64(t.Unpack64()) }
 
 // UIntKey represents a key
 type UIntKey struct {
@@ -216,7 +210,7 @@ func (k *UIntKey) Name() string        { return k.name }
 func (k *UIntKey) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *UIntKey) Of(v uint) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *UIntKey) Of(v uint) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *UIntKey) Get(tags TagMap) uint {
@@ -227,7 +221,7 @@ func (k *UIntKey) Get(tags TagMap) uint {
 }
 
 // From can be used to get a value from a Tag.
-func (k *UIntKey) From(t Tag) uint { return uint(t.packed) }
+func (k *UIntKey) From(t Tag) uint { return uint(t.Unpack64()) }
 
 // UInt8Key represents a key
 type UInt8Key struct {
@@ -244,7 +238,7 @@ func (k *UInt8Key) Name() string        { return k.name }
 func (k *UInt8Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *UInt8Key) Of(v uint8) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *UInt8Key) Of(v uint8) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *UInt8Key) Get(tags TagMap) uint8 {
@@ -255,7 +249,7 @@ func (k *UInt8Key) Get(tags TagMap) uint8 {
 }
 
 // From can be used to get a value from a Tag.
-func (k *UInt8Key) From(t Tag) uint8 { return uint8(t.packed) }
+func (k *UInt8Key) From(t Tag) uint8 { return uint8(t.Unpack64()) }
 
 // UInt16Key represents a key
 type UInt16Key struct {
@@ -272,7 +266,7 @@ func (k *UInt16Key) Name() string        { return k.name }
 func (k *UInt16Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *UInt16Key) Of(v uint16) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *UInt16Key) Of(v uint16) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *UInt16Key) Get(tags TagMap) uint16 {
@@ -283,7 +277,7 @@ func (k *UInt16Key) Get(tags TagMap) uint16 {
 }
 
 // From can be used to get a value from a Tag.
-func (k *UInt16Key) From(t Tag) uint16 { return uint16(t.packed) }
+func (k *UInt16Key) From(t Tag) uint16 { return uint16(t.Unpack64()) }
 
 // UInt32Key represents a key
 type UInt32Key struct {
@@ -300,7 +294,7 @@ func (k *UInt32Key) Name() string        { return k.name }
 func (k *UInt32Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *UInt32Key) Of(v uint32) Tag { return Tag{Key: k, packed: uint64(v)} }
+func (k *UInt32Key) Of(v uint32) Tag { return TagOf64(k, uint64(v)) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *UInt32Key) Get(tags TagMap) uint32 {
@@ -311,7 +305,7 @@ func (k *UInt32Key) Get(tags TagMap) uint32 {
 }
 
 // From can be used to get a value from a Tag.
-func (k *UInt32Key) From(t Tag) uint32 { return uint32(t.packed) }
+func (k *UInt32Key) From(t Tag) uint32 { return uint32(t.Unpack64()) }
 
 // UInt64Key represents a key
 type UInt64Key struct {
@@ -328,7 +322,7 @@ func (k *UInt64Key) Name() string        { return k.name }
 func (k *UInt64Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *UInt64Key) Of(v uint64) Tag { return Tag{Key: k, packed: v} }
+func (k *UInt64Key) Of(v uint64) Tag { return TagOf64(k, v) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *UInt64Key) Get(tags TagMap) uint64 {
@@ -339,7 +333,7 @@ func (k *UInt64Key) Get(tags TagMap) uint64 {
 }
 
 // From can be used to get a value from a Tag.
-func (k *UInt64Key) From(t Tag) uint64 { return t.packed }
+func (k *UInt64Key) From(t Tag) uint64 { return t.Unpack64() }
 
 // Float32Key represents a key
 type Float32Key struct {
@@ -357,7 +351,7 @@ func (k *Float32Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
 func (k *Float32Key) Of(v float32) Tag {
-	return Tag{Key: k, packed: uint64(math.Float32bits(v))}
+	return TagOf64(k, uint64(math.Float32bits(v)))
 }
 
 // Get can be used to get a tag for the key from a TagMap.
@@ -370,7 +364,7 @@ func (k *Float32Key) Get(tags TagMap) float32 {
 
 // From can be used to get a value from a Tag.
 func (k *Float32Key) From(t Tag) float32 {
-	return math.Float32frombits(uint32(t.packed))
+	return math.Float32frombits(uint32(t.Unpack64()))
 }
 
 // Float64Key represents a key
@@ -389,7 +383,7 @@ func (k *Float64Key) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
 func (k *Float64Key) Of(v float64) Tag {
-	return Tag{Key: k, packed: math.Float64bits(v)}
+	return TagOf64(k, math.Float64bits(v))
 }
 
 // Get can be used to get a tag for the key from a TagMap.
@@ -402,7 +396,7 @@ func (k *Float64Key) Get(tags TagMap) float64 {
 
 // From can be used to get a value from a Tag.
 func (k *Float64Key) From(t Tag) float64 {
-	return math.Float64frombits(t.packed)
+	return math.Float64frombits(t.Unpack64())
 }
 
 // StringKey represents a key
@@ -420,7 +414,7 @@ func (k *StringKey) Name() string        { return k.name }
 func (k *StringKey) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *StringKey) Of(v string) Tag { return Tag{Key: k, str: v} }
+func (k *StringKey) Of(v string) Tag { return TagOfString(k, v) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *StringKey) Get(tags TagMap) string {
@@ -431,7 +425,7 @@ func (k *StringKey) Get(tags TagMap) string {
 }
 
 // From can be used to get a value from a Tag.
-func (k *StringKey) From(t Tag) string { return t.str }
+func (k *StringKey) From(t Tag) string { return t.UnpackString() }
 
 // BooleanKey represents a key
 type BooleanKey struct {
@@ -449,11 +443,10 @@ func (k *BooleanKey) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
 func (k *BooleanKey) Of(v bool) Tag {
-	t := Tag{Key: k}
 	if v {
-		t.packed = 1
+		return TagOf64(k, 1)
 	}
-	return t
+	return TagOf64(k, 0)
 }
 
 // Get can be used to get a tag for the key from a TagMap.
@@ -465,7 +458,7 @@ func (k *BooleanKey) Get(tags TagMap) bool {
 }
 
 // From can be used to get a value from a Tag.
-func (k *BooleanKey) From(t Tag) bool { return t.packed > 0 }
+func (k *BooleanKey) From(t Tag) bool { return t.Unpack64() > 0 }
 
 // ErrorKey represents a key
 type ErrorKey struct {
@@ -482,7 +475,7 @@ func (k *ErrorKey) Name() string        { return k.name }
 func (k *ErrorKey) Description() string { return k.description }
 
 // Of creates a new Tag with this key and the supplied value.
-func (k *ErrorKey) Of(v error) Tag { return Tag{Key: k, untyped: v} }
+func (k *ErrorKey) Of(v error) Tag { return TagOfValue(k, v) }
 
 // Get can be used to get a tag for the key from a TagMap.
 func (k *ErrorKey) Get(tags TagMap) error {
@@ -494,6 +487,6 @@ func (k *ErrorKey) Get(tags TagMap) error {
 
 // From can be used to get a value from a Tag.
 func (k *ErrorKey) From(t Tag) error {
-	err, _ := t.untyped.(error)
+	err, _ := t.UnpackValue().(error)
 	return err
 }
diff --git a/internal/telemetry/event/tag.go b/internal/telemetry/event/tag.go
index 5fe40a1e9c..7381cd0b90 100644
--- a/internal/telemetry/event/tag.go
+++ b/internal/telemetry/event/tag.go
@@ -11,7 +11,7 @@ import (
 // Tag holds a key and value pair.
 // It is normally used when passing around lists of tags.
 type Tag struct {
-	Key     Key
+	key     Key
 	packed  uint64
 	str     string
 	untyped interface{}
@@ -20,7 +20,7 @@ type Tag struct {
 // TagMap is the interface to a collection of Tags indexed by key.
 type TagMap interface {
 	// Find returns the tag that matches the supplied key.
-	Find(key interface{}) Tag
+	Find(key Key) Tag
 }
 
 // TagList is the interface to something that provides an iterable
@@ -55,8 +55,45 @@ type tagMapChain struct {
 	maps []TagMap
 }
 
+// TagOfValue creates a new tag from the key and value.
+// This method is for implementing new key types, tag creation should
+// normally be done with the Of method of the key.
+func TagOfValue(k Key, value interface{}) Tag { return Tag{key: k, untyped: value} }
+
+// UnpackValue assumes the tag was built using TagOfValue and returns the value
+// that was passed to that constructor.
+// This method is for implementing new key types, for type safety normal
+// access should be done with the From method of the key.
+func (t Tag) UnpackValue() interface{} { return t.untyped }
+
+// TagOf64 creates a new tag from a key and a uint64. This is often
+// used for non uint64 values that can be packed into a uint64.
+// This method is for implementing new key types, tag creation should
+// normally be done with the Of method of the key.
+func TagOf64(k Key, v uint64) Tag { return Tag{key: k, packed: v} }
+
+// Unpack64 assumes the tag was built using TagOf64 and returns the value that
+// was passed to that constructor.
+// This method is for implementing new key types, for type safety normal
+// access should be done with the From method of the key.
+func (t Tag) Unpack64() uint64 { return t.packed }
+
+// TagOfString creates a new tag from a key and a string.
+// This method is for implementing new key types, tag creation should
+// normally be done with the Of method of the key.
+func TagOfString(k Key, v string) Tag { return Tag{key: k, str: v} }
+
+// UnpackString assumes the tag was built using TagOfString and returns the
+// value that was passed to that constructor.
+// This method is for implementing new key types, for type safety normal
+// access should be done with the From method of the key.
+func (t Tag) UnpackString() string { return t.str }
+
 // Valid returns true if the Tag is a valid one (it has a key).
-func (t Tag) Valid() bool { return t.Key != nil }
+func (t Tag) Valid() bool { return t.key != nil }
+
+// Key returns the key of this Tag.
+func (t Tag) Key() Key { return t.key }
 
 // Format is used for debug printing of tags.
 func (t Tag) Format(f fmt.State, r rune) {
@@ -64,7 +101,7 @@ func (t Tag) Format(f fmt.State, r rune) {
 		fmt.Fprintf(f, `nil`)
 		return
 	}
-	switch key := t.Key.(type) {
+	switch key := t.key.(type) {
 	case *IntKey:
 		fmt.Fprintf(f, "%s=%d", key.Name(), key.From(t))
 	case *Int8Key:
@@ -117,23 +154,23 @@ func (f *tagFilter) Valid(index int) bool {
 func (f *tagFilter) Tag(index int) Tag {
 	tag := f.underlying.Tag(index)
 	for _, f := range f.keys {
-		if tag.Key == f {
+		if tag.Key() == f {
 			return Tag{}
 		}
 	}
 	return tag
 }
 
-func (l tagMap) Find(key interface{}) Tag {
+func (l tagMap) Find(key Key) Tag {
 	for _, tag := range l.tags {
-		if tag.Key == key {
+		if tag.Key() == key {
 			return tag
 		}
 	}
 	return Tag{}
 }
 
-func (c tagMapChain) Find(key interface{}) Tag {
+func (c tagMapChain) Find(key Key) Tag {
 	for _, src := range c.maps {
 		tag := src.Find(key)
 		if tag.Valid() {
diff --git a/internal/telemetry/export/log.go b/internal/telemetry/export/log.go
index f5278eddc3..525c80ef40 100644
--- a/internal/telemetry/export/log.go
+++ b/internal/telemetry/export/log.go
@@ -51,13 +51,13 @@ func (w *logWriter) ProcessEvent(ctx context.Context, ev event.Event, tagMap eve
 		}
 		for index := 0; ev.Valid(index); index++ {
 			tag := ev.Tag(index)
-			if !tag.Valid() || tag.Key == event.Msg || tag.Key == event.Err {
+			if !tag.Valid() || tag.Key() == event.Msg || tag.Key() == event.Err {
 				continue
 			}
 			io.WriteString(w.writer, "\n\t")
-			io.WriteString(w.writer, tag.Key.Name())
+			io.WriteString(w.writer, tag.Key().Name())
 			io.WriteString(w.writer, "=")
-			switch key := tag.Key.(type) {
+			switch key := tag.Key().(type) {
 			case *event.IntKey:
 				w.writer.Write(strconv.AppendInt(buf, int64(key.From(tag)), 10))
 			case *event.Int8Key:
diff --git a/internal/telemetry/export/metric/exporter.go b/internal/telemetry/export/metric/exporter.go
index 56b4fa1609..ad3552fb44 100644
--- a/internal/telemetry/export/metric/exporter.go
+++ b/internal/telemetry/export/metric/exporter.go
@@ -42,7 +42,7 @@ func (e *Config) Exporter(output event.Exporter) event.Exporter {
 			if !tag.Valid() {
 				continue
 			}
-			id := tag.Key
+			id := tag.Key()
 			if list := e.subscribers[id]; len(list) > 0 {
 				for _, s := range list {
 					metrics = append(metrics, s(ev.At, tagMap, tag))
diff --git a/internal/telemetry/export/ocagent/ocagent.go b/internal/telemetry/export/ocagent/ocagent.go
index 217ce9fb68..0d1af1aa38 100644
--- a/internal/telemetry/export/ocagent/ocagent.go
+++ b/internal/telemetry/export/ocagent/ocagent.go
@@ -245,7 +245,7 @@ func convertAttributes(l event.TagList) *wire.Attributes {
 	attributes := make(map[string]wire.Attribute)
 	for {
 		if tag.Valid() {
-			attributes[tag.Key.Name()] = convertAttribute(tag)
+			attributes[tag.Key().Name()] = convertAttribute(tag)
 		}
 		index++
 		if !l.Valid(index) {
@@ -256,7 +256,7 @@ func convertAttributes(l event.TagList) *wire.Attributes {
 }
 
 func convertAttribute(tag event.Tag) wire.Attribute {
-	switch key := tag.Key.(type) {
+	switch key := tag.Key().(type) {
 	case *event.IntKey:
 		return wire.IntAttribute{IntValue: int64(key.From(tag))}
 	case *event.Int8Key: