Okla. Stat. tit. 58 § 334
Every claim shall be signed by the claimant or the claimant's authorized representative. Every claim which is due when presented to the personal representative shall state the exact amount claimed and shall state with reasonable particularity the nature and source of the claim, and if the claim is secured by a security interest, mortgage or other lien which has been filed or recorded according to law, a brief description of such interest, mortgage or lien and of the collateral covered thereby shall be stated in the claim. If the claim be not due when presented, or be contingent, the particulars of such claim must be stated. The personal representative may require satisfactory vouchers or proofs or other evidence to be produced in support of the claim. If the estate is insolvent, no greater rate of interest shall be allowed upon any claim, after the first publication of notice to creditors, than is allowed by law on judgments obtained in the district court.
Okla. Stat. tit. 58, § 334