*810 OPINION
The interpretation of the parties’ intent in a royalty reservation is at the center of this appeal. The reservation appears in a warranty deed from Stewman Ranch, Inc.; O.T. Stewman; and Helen Stewman (the Stewmans) to Dоuble M. Ranch, Ltd. By summary judgment, the trial court held that the Stewmans reserved one-half of the royalty interests owned by the Stewmans at the time of the conveyance rather than one-half of the total royalty. Because we find that the trial court correctly interpreted the warranty deed, we affirm.
The Stewmans conveyed approximately 8,900 acres by warranty deed to Double M. The deed contained reservations for recorded oil, gas, and mineral leases and other recorded reservations of minerals and royalties. The deed also contained the following reservation:
There is, however, excepted and reserved to the Grantors an undivided one-half (½) of the royalties to be paid on the production of oil, gas and other hydrocarbons from the described lands which are presently owned by Grantors for and during the lives of Helen A. Stewman and O.T. Stewman, Jr.; and, upon the death of the survivor of them, this rеtained royalty interest will vest in Grantee, its successors and assigns.
The Stewmans did not own 100% of the royalty interests but, rather, owned undivided interests of varying amounts under the several tracts conveyed. Subsequently, a dispute arose between the parties regarding ownership of the royalties. The Stewmans contended they had reserved one-half of the total mineral interests under the property, while Double M. claimed that the reservation was of one-half of the royаlty interests owned by the Stewmans at the time of the conveyance.
The parties agree that the deed is unambiguous. The determination we are to make, as a matter of law, is whether the Stewmans reserved one-half of all thе royalty attributable to “the described lands” or only one-half of the royalty they owned at the time of the conveyance.
The interpretation of an unambiguous document is a question of law. We review the trial court’s decisiоn de novo.
MCI Telecomm. Corp. v. Tex. Utils. Elec. Co.,
The court’s primary concern is to ascertain the true intention of the parties.
Myers v. Gulf Coast Minerals Mgmt. Corp.,
*811
Double M. urges us to consider canons that have been developed for interpreting deeds and reservations. For example, courts have held that deeds should be construed to convey the greatest estate possible and that reservations should be construed against the grantor. These canons, however, do not apply when the deed is unambiguous.
See Gore Oil Co. v. Roosth, 158
S.W.3d 596, 601 (Tex.App.-Eastland 2005, no pet.) (utilizing canons of construction only after finding warranty deed ambiguous);
Large v. T. Mayfield, Inc.,
Double M. argues that this case can be resolved using the rule adopted in
Duhig v. Peavy-Moore Lumber Co.,
Duhig
is inapplicable to this case because there has been no failure of title. There is a dispute over the interpretation of the mineral reservation, but not all deed construction disрutes constitute a breach of warranty. The warranty serves to indemnify the purchaser against a loss or injury he may sustain by a defect in the seller’s title.
Gibson v. Turner,
Double M.’s
Duhig
argument relies, in part, on the work of its landman, who researched the title to determine what royalty the parties would receive under each of the proffered constructions. Double M. contends that the parties agreed to split the Stewmans’ royalty but that, if the reservation is interpreted to reserve one-half of the total royalty, Double M. will receive no royalty under some tracts and only a minimal interest under the remainder. The parol evidence rule bars our consideration of this analysis because both parties agree that the deed is unambiguous.
Messer v. Johnson,
Unlike Duhig, the Stewmans’ deed did not рurport to convey title that the grantors did not own. The deed here specifically provided that it was subject to the exceptions and reservations contained in it, *812 and those were set out in four paragraphs of the dеed. Consequently, the title that the Stewmans warranted did not include any interest specifically excepted or reserved. Duhig does not apply.
The Stewmans argue that this issue can be resolved by determining whether the reservation refers to “the describеd lands” or the “conveyed lands.” The Stewmans’ argument is based upon a rule of construction developed from two decisions:
Hooks v. Neill,
This case does not fit within the rule developed by Hooks and King because of the unique language contained in the reservation. The difficulty lies with the inclusion of the words: “which are presently owned by Grantors.” If this clause modifies the preceding words: “the described lands,” then the reservation operates to reserve one-half of the total royalties. The Stewman deed describes the tracts being conveyed by survey, abstract, and certificate number. No other interest is similarly described. Under this interpretation, one-half of the royalties from “the described lands” would necessarily mean one-half of the total royalty. If the clause modifies “royalties to be paid,” then the reservation means that-the Stewmans retained only one-half of the royalty they owned at the time of the conveyance.
. [12] Because the Stewmans owned the surface acreage being conveyed, as well as some of the underlying minerals, the clause “which are presently owned by Grantors” logically could refer to either “the described lands” or to “one-half (½) of the royalties to be paid.” To determinе whether the clause “which are presently owned by Grantors” modifies “royalties” or “the described lands,” we refer to basic rules of grammatical construction.
See Reilly v. Rangers Mgmt., Inc.,
One оf the basic rules of grammatical construction is the doctrine of last antecedent. That doctrine provides that relative and qualifying phrases are to be applied to the words or phrases immediately precеding them, unless to do so would impair the meaning of the sentence.
City of Corsicana v. Willmann,
Here, “which are presently owned by Grantors” is a restrictive dependent clause even though it begins with the word “which.” We note that the clause is not set off by commas, as is the case with a nondescriptive or nonrestrictive clause. Although punctuation is not controlling in the interpretation of agreements, it does aid in the interpretation of an instrument.
Criswell v. European Crossroads Shopping Ctr., Ltd.,
If we apply the dependent clause “which arе presently owned by Grantors” to the phrase “one-half (½) of the royalties,” then we have harmonized and have given effect to every part of the agreement; and the clause is not futile, vain, or superfluous. Id. The question before this court is: “What royalties?” Because the dependent clause is an adjective clause, it answers that question in this manner: the royalties that are presently owned by grantor and that are to be paid on the productiоn of oil, gas, and other hydrocarbons from the described lands. In this manner, we have given effect to every word in the agreement in its plain grammatical manner. Simply to apply the doctrine of last antecedent would impair what we perceive the parties actually meant when they made the agreement.
We hold that the clause “which are presently owned by Grantors” refers to and defines “one-half (½) of the royalties” and that the Stewmans resеrved a life estate in one-half of the royalties that they owned at the time of the conveyance, not one-half of the total royalties.
The Stewmans’ issue on appeal is overruled, and the judgment of the trial court is affirmed.
