<PAGE>   1
                                                                    EXHBIT 10.13

                                                                  Grant No. 1658



                                  CLARIFY INC.
                         NOTICE OF GRANT OF STOCK OPTION



               Notice is hereby given of the following option grant (the
"Option") to purchase shares of the Common Stock of Clarify Inc. (the
"Corporation"):

               Optionee:  Jan A. Praisner

               Grant Date:  April 13, 1998

               Vesting Commencement Date:  April 13, 1998

               Exercise Price:  $13.0625 per share

               Number of Option Shares: 225,000 shares

               Expiration Date:  April 12, 2008

               Type of Option:  Non-Statutory Stock Option

               Exercise Schedule: The Option shall become exercisable with
               respect to (i) twenty-five percent (25%) of the Option Shares
               upon Optionee's completion of one (1) year of Service measured
               from the Vesting Commencement Date and (ii) the balance of the
               Option Shares in successive equal monthly installments upon
               Optionee's completion of each of the next thirty-six (36) months
               of Service measured from and after the first anniversary of the
               Vesting Commencement Date. In the event of a Corporate
               Transaction, the provisions of Paragraph 6 shall govern the
               exercisability of the option. In no event shall the Option become
               exercisable for any additional Option Shares after Optionee's
               cessation of Service.

               Optionee hereby acknowledges receipt of a copy of the Option
Summary and Prospectus in the form attached hereto as Exhibit B.

               No Employment or Service Contract. Nothing in this Notice or in
the attached Stock Option Agreement or Plan shall confer upon Optionee any right
to continue in Service for any period of specific duration or interfere with or
otherwise restrict in any way the rights of the Corporation (or any Parent or
Subsidiary employing or retaining Optionee) or of Optionee, which rights are
hereby expressly reserved by each, to terminate Optionee's Service at any time
for any reason, with or without cause.



<PAGE>   2




               Definitions. All capitalized terms in this Notice shall have the
meaning assigned to them in this Notice or in the attached Stock Option
Agreement.



____________, 1998
        Date



                                       CLARIFY INC.


                                       By:
                                          --------------------------------------

                                       Title:
                                             -----------------------------------


                                       -----------------------------------------
                                       OPTIONEE


                                       Address:


                                       -----------------------------------------


ATTACHMENTS
Exhibit A - Stock Option Agreement



                                       2


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                                    EXHIBIT A



<PAGE>   4


                                  CLARIFY INC.
                             STOCK OPTION AGREEMENT



RECITALS

     A.   Optionee is to render valuable services to the Corporation (or a
Parent or Subsidiary), and this Agreement is executed pursuant to, and is
intended to carry out the purposes of the Corporation's grant of an option to
Optionee.

     B.   All capitalized terms in this Agreement shall have the meaning
assigned to them in the attached Appendix.

     NOW, THEREFORE, it is hereby agreed as follows:

     1.   GRANT OF OPTION. The Corporation hereby grants to Optionee, as of the
Grant Date, an option to purchase up to the number of Option Shares specified in
the Grant Notice. The Option Shares shall be purchasable from time to time
during the option term specified in Paragraph 2 at the Exercise Price.

     2.   OPTION TERM. This option shall have a term of ten (10) years measured
from the Grant Date and shall accordingly expire at the close of business on the
Expiration Date, unless sooner terminated in accordance with Paragraph 5 or 6.

     3.   LIMITED TRANSFERABILITY. This option shall be neither transferable nor
assignable by Optionee other than by will or by the laws of descent and
distribution following Optionee's death and may be exercised, during Optionee's
lifetime, only by Optionee. However, this option may be assigned in whole or in
part during Optionee's lifetime in accordance with the terms of a Qualified
Domestic Relations Order. The assigned portion shall be exercisable only by the
person or persons who acquire a proprietary interest in the option pursuant to
such Qualified Domestic Relations Order. The terms applicable to the assigned
portion shall be the same as those in effect for this option immediately prior
to such assignment and shall be set forth in such documents issued to the
assignee as the Board may deem appropriate.

     4.   DATES OF EXERCISE. This option shall become exercisable for the Option
Shares in one or more installments as specified in the Grant Notice. As the
option becomes exercisable for such installments, those installments shall
accumulate and the option shall remain exercisable for the accumulated
installments until the Expiration Date or sooner termination of the option term
under Paragraph 5 or 6.

     5.   CESSATION OF SERVICE. The option term specified in Paragraph 2 shall
terminate (and this option shall cease to be outstanding) prior to the
Expiration Date should any of the following provisions become applicable:

<PAGE>   5

               (i)  Should Optionee cease to remain in Service for any reason
          (other than death, Permanent Disability or Misconduct) while this
          option is outstanding, then Optionee shall have a period of three (3)
          months (commencing with the date of such cessation of Service) during
          which to exercise this option, but in no event shall this option be
          exercisable at any time after the Expiration Date.

               (ii) Should Optionee die while this option is outstanding, then
          the personal representative of Optionee's estate or the person or
          persons to whom the option is transferred pursuant to Optionee's will
          or in accordance with the laws of descent and distribution shall have
          the right to exercise this option. Such right shall lapse and this
          option shall cease to be outstanding upon the earlier of (A) the
          expiration of the twelve (12)- month period measured from the date of
          Optionee's death or (B) the Expiration Date.

               (iii) Should Optionee cease Service by reason of Permanent
          Disability while this option is outstanding, then Optionee shall have
          a period of twelve (12) months (commencing with the date of such
          cessation of Service) during which to exercise this option. In no
          event shall this option be exercisable at any time after the
          Expiration Date.

               (iv) Should Optionee's Service be terminated for Misconduct, then
          this option shall terminate immediately and cease to remain
          outstanding.

               (v)  During the limited period of post-Service exercisability,
          this option may not be exercised in the aggregate for more than the
          number of vested Option Shares for which the option is exercisable at
          the time of Optionee's cessation of Service. Upon the expiration of
          such limited exercise period or (if earlier) upon the Expiration Date,
          this option shall terminate and cease to be outstanding for any vested
          Option Shares for which the option has not been exercised. To the
          extent Optionee is not vested in the Option Shares at the time of
          Optionee's cessation of Service, this option shall immediately
          terminate and cease to be outstanding with respect to those shares.

               (vi) In the event of a Corporate Transaction, the provisions of
          Paragraph 6 shall govern the period for which this option is to remain
          exercisable following Optionee's cessation of Service and shall
          supersede any provisions to the contrary in this paragraph.

     6.   SPECIAL ACCELERATION OF OPTION.

          (a)  In the event of a Corporate Transaction, this option shall become
exercisable for an additional number of shares as if Optionee had been in
Service an additional twelve (12) months at the time of the Corporate
Transaction or, if greater, for 50% of the then

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<PAGE>   6

unexercisable Option Shares. In addition, the exercisability of this option, to
the extent outstanding at such time but not otherwise fully exercisable, shall
automatically accelerate so that this option shall, immediately prior to the
effective date of the Corporate Transaction, become exercisable for any or all
of the Option Shares at the time subject to this option as fully-vested shares
of Common Stock. No such full acceleration of this option pursuant to the
preceding sentence, however, shall occur if and to the extent: (i) this option
is, in connection with the Corporate Transaction, either to be assumed by the
successor corporation (or parent thereof) or to be replaced with a comparable
option to purchase shares of the capital stock of the successor corporation (or
parent thereof) or (ii) this option is to be replaced with a cash incentive
program of the successor corporation which preserves the spread existing on the
Option Shares for which this option is not exercisable at the time of the
Corporate Transaction (the excess of the Fair Market Value of such Option Shares
over the aggregate Exercise Price payable for such shares) and provides for
subsequent pay-out in accordance with the same exercise schedule in effect for
the option pursuant to the option exercise schedule set forth in the Grant
Notice. The determination of option comparability under clause (i) shall be made
by the Compensation Committee of the Board, and such determination shall be
final, binding and conclusive.

          (b)  Immediately following the Corporate Transaction, this option, to
the extent not previously exercised, shall terminate and cease to be
outstanding, except to the extent assumed by the successor corporation (or
parent thereof) in connection with the Corporate Transaction.

          (c)  If this option is assumed in connection with a Corporate
Transaction, then this option shall be appropriately adjusted, immediately after
such Corporate Transaction, to apply to the number and class of securities which
would have been issuable to Optionee in consummation of such Corporate
Transaction had the option been exercised immediately prior to such Corporate
Transaction, and appropriate adjustments shall also be made to the Exercise
Price, provided the aggregate Exercise Price shall remain the same.

          (d)  Upon an Involuntary Termination of Optionee's Service within
eighteen (18) months following a Corporate Transaction in which this option is
assumed or replaced, the exercisability of this option, to the extent
outstanding at such time but not otherwise fully exercisable, shall
automatically accelerate so that this option shall immediately become fully
exercisable for all the Option Shares at the time subject to this option as
fully-vested shares of Common Stock and may be exercised for any or all of those
shares at any time prior to the earlier of (i) the Expiration Date or (ii) the
expiration of the one (1)-year period measured from the effective date of the
Involuntary Termination.

          (e)  This Agreement shall not in any way affect the right of the
Corporation to adjust, reclassify, reorganize or otherwise change its capital or
business structure or to merge, consolidate, dissolve, liquidate or sell or
transfer all or any part of its business or assets.

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<PAGE>   7


     7.   ADJUSTMENT IN OPTION SHARES. Should any change be made to the Common
Stock by reason of any stock split, stock dividend, recapitalization,
combination of shares, exchange of shares or other change affecting the
outstanding Common Stock as a class without the Corporation's receipt of
consideration, appropriate adjustments shall be made to (i) the total number
and/or class of securities subject to this option and (ii) the Exercise Price in
order to reflect such change and thereby preclude a dilution or enlargement of
benefits hereunder.

     8.   STOCKHOLDER RIGHTS. The holder of this option shall not have any
stockholder rights with respect to the Option Shares until such person shall
have exercised the option, paid the Exercise Price and become a holder of record
of the purchased shares.

     9.   MANNER OF EXERCISING OPTION.

          (a)  In order to exercise this option with respect to all or any part
of the Option Shares for which this option is at the time exercisable, Optionee
(or any other person or persons exercising the option) must take the following
actions:

               (i)  Execute and deliver to the Corporation a Notice of Exercise
          for the Option Shares for which the option is exercised.

               (ii) Pay the aggregate Exercise Price for the purchased shares in
          one or more of the following forms:

                    (A)  cash or check made payable to the Corporation;

                    (B)  a promissory note payable to the Corporation, but only
               to the extent authorized by the Compensation Committee of the
               Board in accordance with Paragraph 13;

                    (C)  shares of Common Stock held by Optionee (or any other
               person or persons exercising the option) for the requisite period
               necessary to avoid a charge to the Corporation's earnings for
               financial reporting purposes and valued at Fair Market Value on
               the Exercise Date; or

                    (D)  through a special sale and remittance procedure
               pursuant to which Optionee (or any other person or persons
               exercising the option) shall concurrently provide irrevocable
               written instructions (I) to a Corporation-designated brokerage
               firm to effect the immediate sale of the purchased shares and
               remit to the Corporation, out of the sale proceeds available on
               the settlement date, sufficient funds to cover the aggregate
               Exercise Price payable for the purchased shares plus all
               applicable Federal, state and local income and employment taxes
               required to be withheld by the Corporation by reason of such
               exercise and (II) to the

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<PAGE>   8


               Corporation to deliver the certificates for the purchased shares
               directly to such brokerage firm in order to complete the sale.

                    Except to the extent the sale and remittance procedure is
               utilized in connection with the option exercise, payment of the
               Exercise Price must accompany the Notice of Exercise delivered to
               the Corporation in connection with the option exercise.

               (iii) Furnish to the Corporation appropriate documentation that
          the person or persons exercising the option (if other than Optionee)
          have the right to exercise this option.

               (iv) Make appropriate arrangements with the Corporation (or
          Parent or Subsidiary employing or retaining Optionee) for the
          satisfaction of all Federal, state and local income and employment tax
          withholding requirements applicable to the option exercise.

          (b)  As soon as practical after the Exercise Date, the Corporation
shall issue to or on behalf of Optionee (or any other person or persons
exercising this option) a certificate for the purchased Option Shares, with the
appropriate legends affixed thereto.

          (c)  In no event may this option be exercised for any fractional
shares.

     10.  COMPLIANCE WITH LAWS AND REGULATIONS.

          (a)  The exercise of this option and the issuance of the Option Shares
upon such exercise shall be subject to compliance by the Corporation and
Optionee with all applicable requirements of law relating thereto and with all
applicable regulations of any stock exchange (or the Nasdaq National Market, if
applicable) on which the Common Stock may be listed for trading at the time of
such exercise and issuance.

          (b)  The inability of the Corporation to obtain approval from any
regulatory body having authority deemed by the Corporation to be necessary to
the lawful issuance and sale of any Common Stock pursuant to this option shall
relieve the Corporation of any liability with respect to the non-issuance or
sale of the Common Stock as to which such approval shall not have been obtained.
The Corporation, however, shall use its best efforts to obtain all such
approvals.

     11.  SUCCESSORS AND ASSIGNS. Except to the extent otherwise provided in
Paragraphs 3 and 6, the provisions of this Agreement shall inure to the benefit
of, and be binding upon, the Corporation and its successors and assigns and
Optionee, Optionee's assigns and the legal representatives, heirs and legatees
of Optionee's estate.

     12.  NOTICES. Any notice required to be given or delivered to the
Corporation under the terms of this Agreement shall be in writing and addressed
to the Corporation at its

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principal corporate offices. Any notice required to be given or delivered to
Optionee shall be in writing and addressed to Optionee at the address indicated
below Optionee's signature line on the Grant Notice. All notices shall be deemed
effective upon personal delivery or upon deposit in the U.S. mail, postage
prepaid and properly addressed to the party to be notified.

     13.  FINANCING. The Compensation Committee of the Board may, in its
absolute discretion and without any obligation to do so, permit Optionee to pay
the Exercise Price for the purchased Option Shares by delivering a promissory
note. The terms of any such promissory note (including the interest rate, the
requirements for collateral and the terms of repayment) shall be established by
the Compensation Committee of the Board in its sole discretion.

     14.  GOVERNING LAW. The interpretation, performance and enforcement of this
Agreement shall be governed by the laws of the State of California without
resort to that State's conflict-of-laws rules.

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<PAGE>   10

                                    EXHIBIT I

                               NOTICE OF EXERCISE



     I hereby notify Clarify Inc. (the "Corporation") that I elect to purchase
_________ shares of the Corporation's Common Stock (the "Purchased Shares") at
the option exercise price of $_________ per share (the "Exercise Price")
pursuant to that certain option (the "Option") granted to me on April 13, 1998.

     Concurrently with the delivery of this Exercise Notice to the Corporation,
I shall hereby pay to the Corporation the Exercise Price for the Purchased
Shares in accordance with the provisions of my agreement with the Corporation
(or other documents) evidencing the Option and shall deliver whatever additional
documents may be required by such agreement as a condition for exercise.
Alternatively, I may utilize the special broker-dealer sale and remittance
procedure specified in my agreement to effect payment of the Exercise Price.


                      ,199__
---------------------
Date

<TABLE>
<S>                                    <C>
                                       -----------------------------------------
                                       Optionee

                                       Address:
                                                --------------------------------

                                       -----------------------------------------


Print name in exact manner
it is to appear on the
stock certificate:
                                       -----------------------------------------

Address to which certificate
is to be sent, if different
from address above:
                                       -----------------------------------------

                                       -----------------------------------------

Social Security Number:
                                       -----------------------------------------

Employee Number:
                                       -----------------------------------------

</TABLE>

<PAGE>   11

                                    APPENDIX



     The following definitions shall be in effect under the Agreement:

     A.   AGREEMENT shall mean this Stock Option Agreement.

     B.   BOARD shall mean the Corporation's Board of Directors.

     C.   CODE shall mean the Internal Revenue Code of 1986, as amended.

     D.   COMMON STOCK shall mean the Corporation's common stock.

     E.   CORPORATE TRANSACTION shall mean either of the following
stockholder-approved transactions to which the Corporation is a party:

          (i)  a merger or consolidation in which securities possessing more
     than fifty percent (50%) of the total combined voting power of the
     Corporation's outstanding securities are transferred to a person or persons
     different from the persons holding those securities immediately prior to
     such transaction, or

          (ii) the sale, transfer or other disposition of all or substantially
     all of the Corporation's assets in complete liquidation or dissolution of
     the Corporation.

     F.   CORPORATION shall mean Clarify Inc., a Delaware corporation.

     G.   DOMESTIC RELATIONS ORDER shall mean any judgment, decree or order
(including approval of a property settlement agreement) which provides or
otherwise conveys, pursuant to applicable State domestic relations laws
(including community property laws), marital property rights to any spouse or
former spouse of the Optionee.

     H.   EMPLOYEE shall mean an individual who is in the employ of the
Corporation (or any Parent or Subsidiary), subject to the control and direction
of the employer entity as to both the work to be performed and the manner and
method of performance.

     I. EXERCISE DATE shall mean the date on which the option shall have been
exercised in accordance with Paragraph 9 of the Agreement.

     J.   EXERCISE PRICE shall mean the exercise price per share as specified in
the Grant Notice.

     K.   EXPIRATION DATE shall mean the date on which the option expires as
specified in the Grant Notice.

<PAGE>   12


     L.   FAIR MARKET VALUE per share of Common Stock on any relevant date shall
be determined in accordance with the following provisions:

          (i)  If the Common Stock is at the time traded on the Nasdaq National
     Market, then the Fair Market Value shall be the closing selling price per
     share of Common Stock on the date in question, as the price is reported by
     the National Association of Securities Dealers on the Nasdaq National
     Market or any successor system. If there is no closing selling price for
     the Common Stock on the date in question, then the Fair Market Value shall
     be the closing selling price on the last preceding date for which such
     quotation exists.

          (ii) If the Common Stock is at the time listed on any Stock Exchange,
     then the Fair Market Value shall be the closing selling price per share of
     Common Stock on the date in question on the Stock Exchange determined by
     the Board to be the primary market for the Common Stock, as such price is
     officially quoted in the composite tape of transactions on such exchange.
     If there is no closing selling price for the Common Stock on the date in
     question, then the Fair Market Value shall be the closing selling price on
     the last preceding date for which such quotation exists.

     M.   GRANT DATE shall mean the date of grant of the option as specified in
the Grant Notice.

     N.   GRANT NOTICE shall mean the Notice of Grant of Stock Option
accompanying the Agreement, pursuant to which Optionee has been informed of the
basic terms of the option evidenced hereby.

     O.   INVOLUNTARY TERMINATION shall mean the termination of Optionee's
Service which occurs by reason of:

          (i)  Optionee's involuntary dismissal or discharge by the Corporation
     for reasons other than Misconduct, or

          (ii) Optionee's voluntary resignation following (A) a change in
     Optionee's position with the Corporation (or Parent or Subsidiary employing
     Optionee) which materially reduces Optionee's level of responsibility, (B)
     a reduction in Optionee's level of compensation (including base salary,
     fringe benefits and participation in corporate-performance based bonus or
     incentive programs) by more than fifteen percent (15%) or (C) a relocation
     of Optionee's place of employment by more than fifty (50) miles, provided
     and only if such change, reduction or relocation is effected by the
     Corporation without Optionee's consent.

     P.   MISCONDUCT shall mean the commission of any act of fraud, embezzlement
or dishonesty by Optionee, any unauthorized use or disclosure by Optionee of
confidential

                                      A-2

<PAGE>   13

information or trade secrets of the Corporation (or any Parent or Subsidiary),
or any other intentional misconduct by Optionee adversely affecting the business
or affairs of the Corporation (or any Parent or Subsidiary) in a material
manner. The foregoing definition shall not be deemed to be inclusive of all the
acts or omissions which the Corporation (or any Parent or Subsidiary) may
consider as grounds for the dismissal or discharge of Optionee or any other
individual in the Service of the Corporation (or any Parent or Subsidiary).

     Q.   NON-STATUTORY OPTION shall mean an option not intended to satisfy the
requirements of Code Section 422.

     R.   NOTICE OF EXERCISE shall mean the notice of exercise in the form
attached hereto as Exhibit I.

     S.   OPTION SHARES shall mean the number of shares of Common Stock subject
to the option as specified in the Grant Notice.

     T.   OPTIONEE shall mean the person to whom the option is granted as
specified in the Grant Notice.

     U.   PARENT shall mean any corporation (other than the Corporation) in an
unbroken chain of corporations ending with the Corporation, provided each
corporation in the unbroken chain (other than the Corporation) owns, at the time
of the determination, stock possessing fifty percent (50%) or more of the total
combined voting power of all classes of stock in one of the other corporations
in such chain.

     V.   PERMANENT DISABILITY shall mean the inability of Optionee to engage in
any substantial gainful activity by reason of any medically determinable
physical or mental impairment which is expected to result in death or has lasted
or can be expected to last for a continuous period of twelve (12) months or
more.

     W.   QUALIFIED DOMESTIC RELATIONS ORDER shall mean a Domestic Relations
Order which substantially complies with the requirements of Code Section 414(p).
The Board shall have the sole discretion to determine whether a Domestic
Relations Order is a Qualified Domestic Relations Order.

     X.   SERVICE shall mean the Optionee's performance of services for the
Corporation (or any Parent or Subsidiary) in the capacity of an Employee, a
non-employee member of the board of directors or a consultant or independent
advisor.

     Y.   STOCK EXCHANGE shall mean the American Stock Exchange or the New York
Stock Exchange.

     Z.   SUBSIDIARY shall mean any corporation (other than the Corporation) in
an unbroken chain of corporations beginning with the Corporation, provided each
corporation (other than the last corporation) in the unbroken chain owns, at the
time of the determination, stock possessing fifty percent (50%) or more of the
total combined voting power of all classes of stock in one of the other
corporations in such chain.

                                      A-3