diff --git a/src/FIT.jl b/src/FIT.jl
index cd100b2..e2b3da6 100644
--- a/src/FIT.jl
+++ b/src/FIT.jl
@@ -8,6 +8,4 @@ using .file
 end
 
 using .FIT
-open("test.FIT", "r") do f
-    h = FIT.read_header(f)
-end
\ No newline at end of file
+ffr = FIT.read_file("test.FIT")
\ No newline at end of file
diff --git a/src/file.jl b/src/file.jl
index 7fe0ce0..21200a1 100644
--- a/src/file.jl
+++ b/src/file.jl
@@ -31,7 +31,7 @@ mutable struct RecordHeader
 end
 
 struct FieldDefinition
-    number::UInt8
+    type::AbstractString
     sz_bytes::UInt8
     base_type::Type # TODO: This needs to be translated into an actual base type.
 end
@@ -126,7 +126,7 @@ function decode_header(v::Vector{UInt8})::RecordHeader
     record = blank_header_byte()
     record.definition = v[7] === 0x01
     record.data = !record.definition
-    record.local_mesg_type = sum_bits(v[end-3:end])
+    record.local_mesg_type = sum_bits(v[1:4])
     record
 end
 
@@ -135,9 +135,10 @@ end
 
 Parse a field definition in the definition message into a struct
 """
-function parse_field(bytes::Vector{UInt8})::FieldDefinition
+function parse_field(mesg_type::AbstractString, bytes::Vector{UInt8})::FieldDefinition
+    # TODO the first byte of the field definition, the field num, is definiedre-defined by each mesg definitionn
     FieldDefinition(
-        bytes[1],
+        get_field_description(mesg_type, bytes[1]),
         bytes[2],
         get_base_type(bytes[3])
     )
@@ -153,11 +154,11 @@ function read_record_content!(f::FITFileReader, hdr::RecordHeader)::Union{Defini
     if hdr.definition
         # Read the fixed 5 bytes first.
         def_header_bytes = read_bytes!(f, 5)
+        global_mesg_type = get_mesg_num_string(byte_vec_to_int(def_header_bytes[3:4]))
         def_header_fields = read_bytes!(f, def_header_bytes[end] * 3)
 
-        # Should always be a multiple of 3
-        # TODO: There is a missing byte here that complicates parsing
-        field_definitions = [parse_field(def_header_fields[i:i+2]) for i ∈ 1:3:length(def_header_fields)]
+        # Parse the field. global_mesg_type needed to decode the field number description
+        field_definitions = [parse_field(global_mesg_type, def_header_fields[i:i+2]) for i ∈ 1:3:length(def_header_fields)]
 
         # See if there is developer data
         def_header_developer_flag = read_bytes!(f, 1)
@@ -166,7 +167,6 @@ function read_record_content!(f::FITFileReader, hdr::RecordHeader)::Union{Defini
         end
 
         # Associate the global message type with this local message type.
-        global_mesg_type = get_mesg_num_string(byte_vec_to_int(def_header_bytes[3:4]))
         f.mesg_map[hdr.local_mesg_type] = global_mesg_type
         
         DefinitionBody(
diff --git a/src/mesg_num.jl b/src/mesg_num.jl
index 1903187..9c56e27 100644
--- a/src/mesg_num.jl
+++ b/src/mesg_num.jl
@@ -2,7 +2,7 @@
 
 module mesg_num
 
-export get_mesg_num_string, get_field_definition_string
+export get_mesg_num_string, get_field_definition_string, get_mesg_num, get_field_description
 
 FILE_ID = 0
 CAPABILITIES = 1
@@ -138,14 +138,14 @@ MESG_NUM_MAP = Dict(
     MONITORING => "MONITORING",
     TRAINING_FILE => "TRAINING_FILE",
     HRV => "HRV",
-    ANT_RX => "ANT_RX", 
+    ANT_RX => "ANT_RX",
     ANT_TX => "ANT_TX",
     ANT_CHANNEL_ID => "ANT_CHANNEL_ID",
     LENGTH => "LENGTH",
     MONITORING_INFO => "MONITORING_INFO",
     PAD => "PAD",
     SLAVE_DEVICE => "SLAVE_DEVICE",
-    CONNECTIVITY => "CONNECTIVITY", 
+    CONNECTIVITY => "CONNECTIVITY",
     WEATHER_CONDITIONS => "WEATHER_CONDITIONS",
     WEATHER_ALERT => "WEATHER_ALERT",
     CADENCE_ZONE => "CADENCE_ZONE",
@@ -216,6 +216,16 @@ function get_mesg_num_string(mesg_num::Real)::Union{AbstractString,Nothing}
     end
 end
 
+function get_mesg_num(mesg_type::AbstractString)::Union{Real,Nothing}
+    for (key, value) ∈ MESG_NUM_MAP
+        if value == mesg_type
+            return key
+        end
+    end
+
+    return nothing
+end
+
 FIELD_DEFINITION_MAP = Dict(
     0xFF => "Invalid",
     254 => "MessageIndex",
@@ -230,4 +240,22 @@ function get_field_definition_string(num::Real)::Union{AbstractString,Nothing}
     end
 end
 
+FIELD_DESCRIPTIONS = Dict(FILE_ID => Dict(
+    0 => "type",
+    1 => "manufacturer",
+    2 => "product",
+    3 => "serial_number",
+    4 => "time_created",
+    5 => "number",
+    8 => "product_name"
+))
+
+function get_field_description(mesg_type::AbstractString, field_num::Real)::Union{AbstractString, Nothing}
+    try
+        FIELD_DESCRIPTIONS[get_mesg_num(mesg_type)][field_num]
+    catch
+        "nothing"
+    end
+end
+
 end
\ No newline at end of file