Showing Possession of What You Claim

Written from 35 U.S.C. 112 and MPEP 2163. The statute is law; the MPEP is examination guidance and binds no court. Current as of 22 August 2026.

Read this with Amgen v. Sanofi and Juno v. Kite. Those are courts invalidating claims. This is what the Office tells examiners to look for during examination, which is the earlier and cheaper place to find the same problem.

What it says

The written description requirement asks whether the document shows that the inventor had the invention now claimed. The manual's standard is possession, shown by describing the claimed invention with all its limitations, using words, structures, figures, diagrams and formulas.

The question sounds circular and is not. It is not whether the invention works, or whether it is new. It is whether the application demonstrates that whoever wrote it had the thing the claims now cover.

Two passages in the manual pull in opposite directions, and they have to be read together.

The general rule is a warning about function. An invention "described solely in terms of a method of making and/or its function may lack written descriptive support where there is no described or art-recognized correlation between the disclosed function and the structure(s) responsible for the function."

The software passage runs the other way. The manual carries a Federal Circuit statement that where software constitutes part of a best mode, describing that best mode is satisfied by disclosing the functions of the software, because writing the code is within the skill of the art once the functions are disclosed. That passage concludes that flow charts are not required.

Neither sentence survives being quoted alone. "Flow charts are not required" read by itself tells an engineer their functional write-up is sufficient, and the manual does not say that. The general rule says close to the opposite where no correlation between function and structure has been described or recognized in the art. Both are in the same section for a reason.

The manual also records two things worth knowing: possession alone does not cure a missing description, and there is a presumption of adequate description when an application is filed.

What This Does Not Decide

Whether any description shows possession is exactly the question a page cannot answer. It is a finding made against specific claims and a specific disclosure, and the two passages above mean the answer is not derivable from the format of a document.

It does not say whether your specification shows possession of your claims.
It does not say that functional description is sufficient, and it does not say it is insufficient. Which one applies depends on whether a correlation between function and structure is described or recognized in the art.
It is not law. The MPEP is examiner guidance.
It does not cover enablement, which is a separate requirement asking a different question.

Educational, not legal advice. Whether a disclosure supports a claim is work for a registered patent practitioner with both documents in front of them.

Sources

35 U.S.C. 112(a); MPEP 2163, Guidelines for the Examination of Patent Applications Under the 35 U.S.C. 112(a) Written Description Requirement
Fonar Corp. v. General Electric Co., 107 F.3d 1543 (Fed. Cir. 1997), as carried in the manual
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