How to check written-description support before claiming a competitor’s product

Motive is not the problem. There is “nothing improper” in amending or inserting claims “intended to cover a competitor’s product the applicant’s attorney has learned about during the prosecution of a patent application” (Kingsdown Medical Consultants v. Hollister, Fed. Cir. 1988). The condition is support. Broadening to cover a competitor is proper “as long as the disclosure supports the broadened claims” (Liebel-Flarsheim v. Medrad, 358 F.3d 898, 909 (Fed. Cir. 2004)).

Product-driven claims get extra scrutiny. In Quake v. Lo, 928 F.3d 1365 (Fed. Cir. 2019), Quake cancelled his target-sequence claims and added random-MPS claims after Lo’s application on random MPS published. The court affirmed that the new claims lacked written description:

“‘[T]he purpose of the written description requirement is to prevent an applicant from later asserting that he invented that which he did not,’ and the requirement is particularly important when, as here, claims are added later during prosecution in response to development by others.” (slip op. at 15)

Allowance will not rescue a gap. Mondis Technology v. LG Electronics (Fed. Cir. Aug. 8, 2025, precedential) reversed a jury verdict and held two claims invalid for lack of written description. The limitation had been added to overcome prior art, not to reach a competitor. The court held that the examiner’s allowance of that amendment is not, by itself, substantial evidence of § 112 support: “If it did, there would rarely be a situation where an issued patent could later be invalidated for lack of written description.” (slip op. at 15)

Google LLC v. Sonos, Inc. (Fed. Cir. Aug. 28, 2025) also touched written description. It is nonprecedential. It reversed the rulings that two Sonos patents were invalid for lack of written description and unenforceable for laches. It illustrates a result on its facts; it does not lower the bar. More in our Sonos v. Google explainer.

The question is whether the specification shows that, “as of the filing date sought, the inventor was in possession of the invention as now claimed” (MPEP 2163.02). Six steps turn that into a record you can defend.

1. Start from the specification as filed

Support is measured against the disclosure on the filing date. Pull the as-filed specification, claims and drawings from the file wrapper. The published application is a different document. It is based on the filed papers, but it may also reflect a substitute specification or amendments entered before publication (37 CFR 1.215(a)). Its paragraph numbering and text can therefore differ from the filed version. Neither is wrong; they answer different questions. Cite the as-filed text, and say which version your paragraph numbers come from.

2. List the product features from public documentation

Use the competitor’s product pages, manuals, help articles and release notes. Record the URL and the date accessed for each feature. Write each feature as a short neutral sentence. Do not assume how a feature works internally if the documentation does not say.

3. Map each proposed claim element to paragraphs and figures

Split the draft claim into elements. For each one, cite the paragraph and any figure, and quote the words that carry the support. A citation without a quote hides how thin the support is. Search the original claims and abstract too; they are part of the disclosure.

4. Grade the support

• Strong: the specification uses the same words as the element.
• Moderate: the element is implied by a passage read with a figure, but not stated.
• Weak: support rests on inference only, such as a generic phrase or what a skilled reader might add.

Literal wording is not required, but new limitations need “express, implicit, or inherent” support (MPEP 2163). The grades are our working scale for triage, not a legal standard.

5. Redraft or drop elements without support

Where an element is weak, rewrite it in the specification’s own terms, even if that narrows coverage. If no supported wording reaches the product feature, drop the element. A narrower claim that holds is worth more than a broad one that fails under § 112.

6. Check the chain

A continuation claim gets an ancestor’s filing date only if that ancestor supports it, and so does every application in between. MPEP 2163 lists entitlement to an earlier date under 35 U.S.C. 120 as a written-description question. Repeat step 3 against each ancestor whose date you need, especially across a continuation-in-part. If the support first appears later, the claim takes the later date.

One row per element: the claim text, the as-filed support with its grade and quote, and the public product documentation it may correspond to. Weak rows stay in the map. Here the signal-strength element is redrafted around a touch sensor the text does describe, and the fingerprint element is dropped. The chain check then shows that the redrafted element can reach back only to 2019.

1. Claiming the genus from a species. The specification describes one embodiment and the claim covers the whole category the product falls in. A genus needs a representative number of species or identifying characteristics, and a genus disclosure may not support a subgenus or species either (In re Smith, as discussed in MPEP 2163).
2. Functional language without structure. The claim recites the result the product achieves, such as “configured to determine proximity,” and the specification never says how. “[D]escribing a composition by its function alone typically will not suffice” (MPEP 2163, citing Eli Lilly). Apply the same caution to any element defined only by its result.
3. Combining embodiments. Each element appears somewhere, but never together. An examiner can reject a claim because the specification does not describe “their combination,” even where it lists each element (Hyatt v. Dudas, as discussed in MPEP 2163). Look for a passage that joins them, or blaze marks that point to the combination.
4. Relying on figures without text. Drawings alone can provide a written description (Vas-Cath, quoted in MPEP 2163). But a figure seldom shows a threshold, a sequence or a purpose. If the element depends on what the figure means rather than what it shows, grade it weak.
5. Numbering mismatch. The map cites paragraph numbers from the published application while the argument rests on the as-filed text, or the reverse. Where the two differ, a cite can point to the wrong passage. Pick one version, label it, and quote the words.

• The element map, with every element graded and quoted, including the weak rows.
• The redrafts and drops, with the reason for each.
• The chain check: the earliest date each claim can claim, and why.
• The product sources, with URLs and dates accessed.

Keep the language neutral. The right conclusion is that the specification may support claims covering a feature described in public documentation. A pending application has no enforceable claims. Whether the support is adequate, and whether to file, is for your registered patent practitioner. The overall strategy and timing are in continuation strategy for competitor products, and our method is set out in how it works.