numbers, IDs & dates

silk normalizes the text you send before it synthesizes, so numbers, money, dates, and IDs come out right. Rs 2,45,600 is read as “two lakh forty five thousand six hundred rupees”, and 09/03/2025 as “ninth March two thousand twenty five”. you write text the normal way. there is one thing you decide: which digits should be read one at a time. wrap those in double quotes. write everything else plainly. normalization runs by default. set "normalization": false on a request to send your text through untouched.

the one rule

a run of digits can be read two ways, and only you know which you mean.

you want it read as	how to write it	silk speaks
a digit-by-digit id (OTP, phone, account, card, PAN, GSTIN, vehicle, coupon, tracking)	wrap it in double quotes `"…"`	`"482093"` reads as four eight two zero nine three
a quantity (prices, counts, years, scores)	write it plainly	`3400` reads as three thousand four hundred

currency symbols, %, dates, and times are picked up on their own. write them the natural way.

why quotes? a bare 8123456789 could be a phone number or a very large count. rather than guess, silk spells out what you put in quotes and reads everything else as a number. quoting is how you tell it which one you meant.

here it is in one request:

curl -X POST https://silk-api.rumik.ai/v1/tts \
  -H "Authorization: Bearer rk_live_•••••••••" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "muga",
    "text": "[neutral] Aapka OTP \"482093\" hai. Rs 2,45,600 debit hue 09/03/2025 ko."
  }' --output out.wav
# speaks: "…OTP four eight two zero nine three hai. two lakh forty five thousand six
#          hundred rupees debit hue ninth March two thousand twenty five ko."

quick reference

data	write it as	spoken
amount (INR)	`Rs 2,45,600`	two lakh forty five thousand six hundred rupees
amount + paise	`Rs 89.75`	eighty nine rupees and seventy five paise
foreign currency	`$45` · `€60` · `£12` · `¥5000`	forty five dollars · sixty euros · twelve pounds · five thousand yen
percentage	`25%` · `7.5%`	twenty five percent · seven point five percent
decimal	`3.2`	three point two
plain number	`3400`	three thousand four hundred
date	`09/03/2025`	ninth March two thousand twenty five
time (24h)	`18:45` · `07:15`	six forty five PM · seven fifteen AM
OTP / PIN	`"482093"` · `"0071"`	four eight two zero nine three · zero zero seven one
phone	`"8123456789"`	eight one two three four five six seven eight nine
phone (+91)	`plus "918123456789"`	plus nine one eight one two three…
account	`"000723145589"`	zero zero zero seven two three…
card ending	`ending "6042"`	ending six zero four two
PAN	`"FGHIJ5678K"`	F G H I J five six seven eight K
GSTIN	`"27FGHIJ5678K1Z3"`	two seven F G H I J … one Z three
vehicle	`"MH12AB4567"`	M H one two A B four five six seven
pincode	`"411045"`	four one one zero four five
coupon / order	`"FEST50"` · `"TRK44120983"`	F E S T five zero · T R K four four one two…
turn off	`"normalization": false`	(raw text, unchanged)

numbers & money

write quantities plainly. silk handles indian grouping (lakh/crore), decimals, and currency symbols on its own. no quotes.

write	spoken
`3400`	three thousand four hundred
`2,45,600`	two lakh forty five thousand six hundred
`3.2`	three point two
`Rs 750` or `Rs750`	seven hundred fifty rupees
`Rs 89.75`	eighty nine rupees and seventy five paise
`Rs 2,00,00,000`	two crore rupees
`$18.40`	eighteen dollars and forty cents

currency symbols: ₹, Rs, Rs., INR, $, €, £, ¥, with or without a space before the amount. do

write Rs 2,45,600. the indian comma grouping is read as lakh/crore.
put the symbol before the amount ($45, not 45$).

don’t

don’t quote an amount. "3400" reads as “three four zero zero”, not the price.

percentages, decimals & time

write	spoken
`25%`	twenty five percent
`7.5%`	seven point five percent
`18:45`	six forty five PM
`07:15`	seven fifteen AM
`06:05`	six oh five AM
`22:30`	ten thirty PM

time is read 24-hour to 12-hour with AM/PM. use a period for decimals (3.2), never a comma.

dates

write DD/MM/YYYY or DD-MM-YY (india, day first). silk reads an ordinal day, then the month name, then the year.

write	spoken
`09/03/2025`	ninth March two thousand twenty five
`01-12-24`	first December two thousand twenty four
`7/6/2025`	seventh June two thousand twenty five

use 4-digit years for anything historical or ambiguous. 24/7 and 3-2-1 are not read as dates; they come out as their numbers.

IDs, always quote

put any identifier in double quotes. digits turn into words, letters stay as letters, separators (spaces, -, /) are dropped, and leading zeros are kept.

type	write	spoken
OTP / PIN	`"482093"` · `"0071"`	four eight two zero nine three · zero zero seven one
phone	`"8123456789"`	eight one two three four five six seven eight nine
toll-free	`"18002094321"`	one eight zero zero two zero nine four three two one
account	`"000723145589"`	zero zero zero seven two three one four five five eight nine
account (grouped)	`"5231 7789 4402 1176"`	five two three one seven seven eight nine …
aadhaar	`"5210 8834 9071"`	five two one zero eight eight three four nine zero seven one
card ending	`ending "6042"`	ending six zero four two
PAN	`"FGHIJ5678K"`	F G H I J five six seven eight K
GSTIN	`"27FGHIJ5678K1Z3"`	two seven F G H I J five six seven eight K one Z three
vehicle	`"MH12AB4567"` or `"MH-12-AB-4567"`	M H one two A B four five six seven
pincode	`"411045"`	four one one zero four five
coupon	`"FEST50"`	F E S T five zero
order / tracking	`"TRK44120983"`	T R K four four one two zero nine eight three

phone numbers with a country code

write the + as the word plus, and quote the digits:

Call plus "918123456789"   →   "…plus nine one eight one two three…"

writing "+918123456789" won’t work; the + inside the quotes isn’t spelled cleanly.

per-model notes

the rules above are the same for both models. these are the only differences. muga. your [tone] tag stays at the very start. normalization leaves tags and <events> alone, so tagging and normalizing never interfere with each other.

[excited] Aapko 3400 reward points mile hain, coupon "FEST50" abhi use karo!

mulberry. there are no tone tags to place, the voice comes from description. normalization only ever touches text, so your description reaches the model exactly as you wrote it.

Aapka refund Rs 1,899 process ho gaya. Reference "RFN20915" hai.

edge cases & gotchas

digits stuck to letters are left alone. B2B, COVID19, 12kg are never split.
a quoted sentence isn’t spelled out. "see you at 400" reads “see you at four hundred”, not letter by letter. only clean identifiers (every token has a digit) get spelled.
leading zeros survive only inside quotes. "0083" reads “zero zero eight three”; an unquoted 0083 becomes “eighty three”.
ranges: 4-6 reads “four-six”. write 4 to 6 if you want the word “to”.
running the same text through twice is safe; normalized text stays as it is.

turning normalization off

set "normalization": false and silk reads your text as-is. nothing is spelled out or converted. here is the same input both ways:

// default (on): the quoted OTP is spelled out
{ "model": "muga", "text": "[neutral] Aapka OTP \"482093\" hai." }
// speaks: "…OTP four eight two zero nine three hai."

// off: the model gets the text untouched and reads it however it reads it
{ "model": "muga", "text": "[neutral] Aapka OTP \"482093\" hai.", "normalization": false }
// speaks: "…OTP <read by the model, not spelled out> hai."

reach for it when your text is already in the exact spoken form you want, or when you need full control over how something is pronounced.

documentation

SDK

integrations

cookbook

API reference

the one rule

quick reference

numbers & money

percentages, decimals & time

dates

IDs, always quote

phone numbers with a country code

per-model notes

edge cases & gotchas

turning normalization off

​the one rule

​quick reference

​numbers & money

​percentages, decimals & time

​dates

​IDs, always quote

​phone numbers with a country code

​per-model notes

​edge cases & gotchas

​turning normalization off

the one rule

quick reference

numbers & money

percentages, decimals & time

dates

IDs, always quote

phone numbers with a country code

per-model notes

edge cases & gotchas

turning normalization off