HMAC-SHA1-128 parameters
There's not a word about the data to authenticate! Update: we are told that's data from a row in database with 4 different columns: Date(YYYY-MM-DD), Time (hh:mm:ss), String(xxxxx), Number (1000.00). It is of paramount importance to specify how this data is transformed into byte before entering HMAC. Concatenation would be dangerous for the last two fields, because in digitsfollow12 34.56 and digitsfollow123 4.56 would give the same MAC.

The hash you want to specify is usually designated SHA-1, not SHA1.

SHA-1 is obsolete, even though when combined with HMAC it remains safe and thus tolerated. A modern replacement would be SHA-256 or SHA-512, followed by truncation of the final HMAC result if a 160-bit output is desired.

The data block size B is redundant with specifying SHA-1, and will need to be kept in sync with the hash. I would suppress that.

Ipad and Opad, and their repetition count, are redundant with the specification of HMAC. I would suppress that.

"Charset = UTF-8" does not make sense to me, unless you want some encoding (like Base-64), or it applies to the data to authenticate, in which case that should be told.

It is not specified how various parameters are passed: array of chars, string, and nature of that; and if the length (e.g. of data to authenticate) is separate or some attribute of an object, and in what unit (bytes, bits), and the maximum. It is not told wether data to authenticate is passed in one block or iteratively.

Giving an example in a spec helps immensely.