MPEP 2163: Written Description Requirement

Answer in brief

MPEP 2163 requires the specification to describe the claimed invention in enough detail to show the inventor had possession of it at the time of filing. It applies to original claims and, most often, to amended or new claims that may add new matter.

What MPEP 2163 covers

Written description is separate from enablement: an inventor can teach how to make something without showing possession of what is claimed.

Possession can be shown through words, structures, figures, diagrams and formulas.
Genus claims need a representative number of species or common structural features.
Typical problems arise with amended claims, broadened claims, and claimed ranges not described in the original disclosure (2163.03, 2163.05).
The examiner bears the initial burden of explaining why the disclosure does not reasonably convey possession.

How examiners use it

Written description rejections are common after amendments. The fix is to point to support in the original disclosure, or cancel the unsupported language.

On the patent bar

Know that written description and enablement are separate requirements, and that adding unsupported claim language is new matter.

Read the full text

Official title: Guidelines for the Examination of Patent Applications Under the 35 U.S.C. 112(a) or Pre-AIA 35 U.S.C. 112, first paragraph, “Written Description” Requirement [R-01.2024].

Read MPEP 2163 in full on Wysebridge ↗

Or at the source: USPTO MPEP § 2163.

Questions & answers

What is the written description requirement?

Under 35 U.S.C. 112(a), the specification must describe the claimed invention well enough that a person skilled in the art would recognize the inventor had possession of it when the application was filed.

Sources for this entry

USPTO — MPEP § 2163 USPTO
Official text of this section, Ninth Edition, Revision 01.2024.
Wysebridge MPEP Center Wysebridge (publisher of this site)
The full MPEP (9th Ed., Rev. 01.2024) free to read, with Wysebridge's estimated patent bar weight for each chapter.

Practical guidance is original editorial content. Company-published figures are the company's own claims and are labeled as such.

Continue this reading path

MPEP 2164: Enablement and the Wands Factors MPEP 2173: Indefiniteness Under 35 U.S.C. 112(b)MPEP 714: Amendments

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Cite or share this entry

MPEP.net. “MPEP 2163: Written Description Requirement.” Wysebridge Reference. Content reviewed 9 November 2026.
https://mpep.net/mpep-2163/