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+<!--
+**Note:** When your KEP is complete, all of these comment blocks should be removed.
+
+To get started with this template:
+
+- [X] **Pick a hosting SIG.**
+  Make sure that the problem space is something the SIG is interested in taking
+  up. KEPs should not be checked in without a sponsoring SIG.
+- [X] **Create an issue in kubernetes/enhancements**
+  When filing an enhancement tracking issue, please make sure to complete all
+  fields in that template. One of the fields asks for a link to the KEP. You
+  can leave that blank until this KEP is filed, and then go back to the
+  enhancement and add the link.
+- [X] **Make a copy of this template directory.**
+  Copy this template into the owning SIG's directory and name it
+  `NNNN-short-descriptive-title`, where `NNNN` is the issue number (with no
+  leading-zero padding) assigned to your enhancement above.
+- [X] **Fill out as much of the kep.yaml file as you can.**
+  At minimum, you should fill in the "Title", "Authors", "Owning-sig",
+  "Status", and date-related fields.
+- [X] **Fill out this file as best you can.**
+  At minimum, you should fill in the "Summary" and "Motivation" sections.
+  These should be easy if you've preflighted the idea of the KEP with the
+  appropriate SIG(s).
+- [X] **Create a PR for this KEP.**
+  Assign it to people in the SIG who are sponsoring this process.
+- [ ] **Merge early and iterate.**
+  Avoid getting hung up on specific details and instead aim to get the goals of
+  the KEP clarified and merged quickly. The best way to do this is to just
+  start with the high-level sections and fill out details incrementally in
+  subsequent PRs.
+
+Just because a KEP is merged does not mean it is complete or approved. Any KEP
+marked as `provisional` is a working document and subject to change. You can
+denote sections that are under active debate as follows:
+
+```
+<<[UNRESOLVED optional short context or usernames ]>>
+Stuff that is being argued.
+<<[/UNRESOLVED]>>
+```
+
+When editing KEPS, aim for tightly-scoped, single-topic PRs to keep discussions
+focused. If you disagree with what is already in a document, open a new PR
+with suggested changes.
+
+One KEP corresponds to one "feature" or "enhancement" for its whole lifecycle.
+You do not need a new KEP to move from beta to GA, for example. If
+new details emerge that belong in the KEP, edit the KEP. Once a feature has become
+"implemented", major changes should get new KEPs.
+
+The canonical place for the latest set of instructions (and the likely source
+of this file) is [here](/keps/NNNN-kep-template/README.md).
+
+**Note:** Any PRs to move a KEP to `implementable`, or significant changes once
+it is marked `implementable`, must be approved by each of the KEP approvers.
+If none of those approvers are still appropriate, then changes to that list
+should be approved by the remaining approvers and/or the owning SIG (or
+SIG Architecture for cross-cutting KEPs).
+-->
+# KEP-NNNN: Your short, descriptive title
+
+<!--
+This is the title of your KEP. Keep it short, simple, and descriptive. A good
+title can help communicate what the KEP is and should be considered as part of
+any review.
+-->
+
+<!--
+A table of contents is helpful for quickly jumping to sections of a KEP and for
+highlighting any additional information provided beyond the standard KEP
+template.
+
+Ensure the TOC is wrapped with
+  <code>&lt;!-- toc --&rt;&lt;!-- /toc --&rt;</code>
+tags, and then generate with `hack/update-toc.sh`.
+-->
+
+<!-- toc -->
+- [Release Signoff Checklist](#release-signoff-checklist)
+- [Summary](#summary)
+- [Motivation](#motivation)
+  - [Goals](#goals)
+  - [Non-Goals](#non-goals)
+- [Proposal](#proposal)
+  - [Enum Pattern](#enum-pattern)
+  - [Enum Tag](#enum-tag)
+  - [Detect Possible Enum Types](#detect-possible-enum-types)
+  - [Notes/Constraints/Caveats (Optional)](#notesconstraintscaveats-optional)
+  - [Risks and Mitigations](#risks-and-mitigations)
+- [Design Details](#design-details)
+  - [OpenAPI v2 Breakage](#openapi-v2-breakage)
+  - [Test Plan](#test-plan)
+  - [Graduation Criteria](#graduation-criteria)
+    - [Alpha](#alpha)
+    - [Beta](#beta)
+    - [Stable](#stable)
+  - [Upgrade / Downgrade Strategy](#upgrade--downgrade-strategy)
+  - [Version Skew Strategy](#version-skew-strategy)
+- [Production Readiness Review Questionnaire](#production-readiness-review-questionnaire)
+  - [Feature Enablement and Rollback](#feature-enablement-and-rollback)
+  - [Rollout, Upgrade and Rollback Planning](#rollout-upgrade-and-rollback-planning)
+  - [Monitoring Requirements](#monitoring-requirements)
+  - [Dependencies](#dependencies)
+  - [Scalability](#scalability)
+  - [Troubleshooting](#troubleshooting)
+- [Implementation History](#implementation-history)
+- [Drawbacks](#drawbacks)
+- [Alternatives](#alternatives)
+  - [Directly into OpenAPI v2](#directly-into-openapi-v2)
+<!-- /toc -->
+
+## Release Signoff Checklist
+
+<!--
+**ACTION REQUIRED:** In order to merge code into a release, there must be an
+issue in [kubernetes/enhancements] referencing this KEP and targeting a release
+milestone **before the [Enhancement Freeze](https://git.k8s.io/sig-release/releases)
+of the targeted release**.
+
+For enhancements that make changes to code or processes/procedures in core
+Kubernetes—i.e., [kubernetes/kubernetes], we require the following Release
+Signoff checklist to be completed.
+
+Check these off as they are completed for the Release Team to track. These
+checklist items _must_ be updated for the enhancement to be released.
+-->
+
+Items marked with (R) are required *prior to targeting to a milestone / release*.
+
+- [X] (R) Enhancement issue in release milestone, which links to KEP dir in [kubernetes/enhancements] (not the initial KEP PR)
+- [X] (R) KEP approvers have approved the KEP status as `implementable`
+- [X] (R) Design details are appropriately documented
+- [ ] (R) Test plan is in place, giving consideration to SIG Architecture and SIG Testing input (including test refactors)
+  - [ ] e2e Tests for all Beta API Operations (endpoints)
+  - [ ] (R) Ensure GA e2e tests for meet requirements for [Conformance Tests](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/conformance-tests.md) 
+  - [ ] (R) Minimum Two Week Window for GA e2e tests to prove flake free
+- [ ] (R) Graduation criteria is in place
+  - [ ] (R) [all GA Endpoints](https://github.com/kubernetes/community/pull/1806) must be hit by [Conformance Tests](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/conformance-tests.md) 
+- [ ] (R) Production readiness review completed
+- [ ] (R) Production readiness review approved
+- [ ] "Implementation History" section is up-to-date for milestone
+- [ ] User-facing documentation has been created in [kubernetes/website], for publication to [kubernetes.io]
+- [ ] Supporting documentation—e.g., additional design documents, links to mailing list discussions/SIG meetings, relevant PRs/issues, release notes
+
+<!--
+**Note:** This checklist is iterative and should be reviewed and updated every time this enhancement is being considered for a milestone.
+-->
+
+[kubernetes.io]: https://kubernetes.io/
+[kubernetes/enhancements]: https://git.k8s.io/enhancements
+[kubernetes/kubernetes]: https://git.k8s.io/kubernetes
+[kubernetes/website]: https://git.k8s.io/website
+
+## Summary
+
+<!--
+This section is incredibly important for producing high-quality, user-focused
+documentation such as release notes or a development roadmap. It should be
+possible to collect this information before implementation begins, in order to
+avoid requiring implementors to split their attention between writing release
+notes and implementing the feature itself. KEP editors and SIG Docs
+should help to ensure that the tone and content of the `Summary` section is
+useful for a wide audience.
+
+A good summary is probably at least a paragraph in length.
+
+Both in this section and below, follow the guidelines of the [documentation
+style guide]. In particular, wrap lines to a reasonable length, to make it
+easier for reviewers to cite specific portions, and to minimize diff churn on
+updates.
+
+[documentation style guide]: https://github.com/kubernetes/community/blob/master/contributors/guide/style-guide.md
+-->
+
+As a sub-KEP of [KEP-2896 OpenAPI v3](https://github.com/kubernetes/enhancements/issues/2896),
+this KEP defines Enum Types support for OpenAPI. Currently, types in our API have fields
+that are actually enums but represented as plain string. This KEP proposes a `+enum`
+annotation to type aliases that represent enums. The OpenAPI generator will have
+the capability to recognize the annotation and auto-detect possible values for an enum. 
+
+## Motivation
+
+<!--
+This section is for explicitly listing the motivation, goals, and non-goals of
+this KEP.  Describe why the change is important and the benefits to users. The
+motivation section can optionally provide links to [experience reports] to
+demonstrate the interest in a KEP within the wider Kubernetes community.
+
+[experience reports]: https://github.com/golang/go/wiki/ExperienceReports
+-->
+
+Currently, types that are actually enums are represented as plain strings. For example,
+here is the definition of `Protocol`, which must be one of `TCP`, `UDP`, and `SCTP`.
+```go
+package core
+// ...
+
+// Protocol defines network protocols supported for things like container ports.
+type Protocol string
+
+const (
+	// ProtocolTCP is the TCP protocol.
+	ProtocolTCP Protocol = "TCP"
+	// ProtocolUDP is the UDP protocol.
+	ProtocolUDP Protocol = "UDP"
+	// ProtocolSCTP is the SCTP protocol.
+	ProtocolSCTP Protocol = "SCTP"
+)
+
+// ContainerPort represents a network port in a single container
+type ContainerPort struct {
+  // ...
+
+  // Required: Supports "TCP", "UDP" and "SCTP"
+  // +optional
+  Protocol Protocol
+  
+  // ...
+}
+```
+
+In order to convey that the `Protocol` type is an enum, every field of the type 
+have to comment its values like `ContainerPort` does. The same goes for validation - 
+protocol being one of "TCP", "UDP", and "SCTP" is duplicated among the code base.
+
+Tools and UIs can also benefit from the additional piece of information. For example,
+Protocol can be shown as a dropdown of possible values instead of a textbox.
+The user no longer needs to see an error of invalid value after submits the request.
+
+### Goals
+
+<!--
+List the specific goals of the KEP. What is it trying to achieve? How will we
+know that this has succeeded?
+-->
+
+- Add an annotation that indicates a field as an enum.
+- Make the Kubernetes OpenAPI generator recognize the annotation.
+- Auto-detect possible values of an enum type.
+- Detect and annotate enum types in all built-in types. 
+
+### Non-Goals
+
+<!--
+What is out of scope for this KEP? Listing non-goals helps to focus discussion
+and make progress.
+-->
+
+This KEP does not require removal of existing validation of enum types. While OpenAPI-based
+of enum types can simplify this type of validation, retiring custom-made validations is out
+of scope.
+
+This proposal does not intend to change the enum syntax for third-party tools like `kubebuilder`.
+The implementation should only suggest changes to internal APIs. 
+
+## Proposal
+
+As part of the OpenAPI v3 KEP, when generating OpenAPI schema,
+the de facto enum types should be reflected as enums in the resulting schema.
+We define enum types with following properties:
+- All enum types are closed, i.e., the type includes a finite number of possible values.
+- All enum types should be string. There can be no enum integers, floats, etc
+
+Additionally, This KEP makes the following assumptions on the implementation:
+- All enum types have their own type alias. i.e. , no raw string enums.
+- The canonical definition of a type is written in go and follows the standard 
+  Kubernetes convention.
+
+### Enum Pattern
+
+The Enum Pattern of a type, appearing in a go source file, is defined as follows:
+```go
+package internal
+
+// FooType define sa type alias, underlying type must be string
+type FooType string
+
+// in the same package, define constants with the alias
+const (
+    BarConst FooType = "Bar"
+    BazConst FooType = "Baz"
+)
+
+// in one or more resources or nested objects, one of the field is of 
+// the defined alias type.
+
+// ExampleResource should refer FooType
+type ExampleResource struct {
+    FooField FooType
+}
+
+```
+
+### Enum Tag
+The Enum Tag is the annotation `// +enum` that must be in the closest comment blocks
+of an enum type following Enum Pattern.
+
+```go
+package internal
+
+// FooType define sa type alias, underlying type must be string
+// +enum
+type FooType string
+```
+
+An actual example looks like
+```go
+package core
+
+// Protocol defines network protocols supported for things like container ports.
+// +enum
+type Protocol string
+```
+
+### Detect Possible Enum Types
+
+A new API rule will be added to `kube-openapi` that warns about detected Enum Pattern
+without the enum tag. If, in a rare situation, the detected type is not an enum, the user can
+add an exception in `/api/api-rules/`.
+
+<!--
+This is where we get down to the specifics of what the proposal actually is.
+This should have enough detail that reviewers can understand exactly what
+you're proposing, but should not include things like API designs or
+implementation. What is the desired outcome and how do we measure success?.
+The "Design Details" section below is for the real
+nitty-gritty.
+-->
+
+### Notes/Constraints/Caveats (Optional)
+
+<!--
+What are the caveats to the proposal?
+What are some important details that didn't come across above?
+Go in to as much detail as necessary here.
+This might be a good place to talk about core concepts and how they relate.
+-->
+
+Not all types following the Enum Pattern are actually enum types. Here is a counter-example.
+```go
+package core
+
+// StorageMedium defines ways that storage can be allocated to a volume.
+type StorageMedium string
+
+// These are the valid value for StorageMedium
+const (
+  StorageMediumDefault         StorageMedium = ""           // use whatever the default is for the node
+  StorageMediumMemory          StorageMedium = "Memory"     // use memory (tmpfs)
+  StorageMediumHugePages       StorageMedium = "HugePages"  // use hugepages
+  StorageMediumHugePagesPrefix StorageMedium = "HugePages-" // prefix for full medium notation HugePages-<size>
+)
+```
+
+Here, `StorageMedium` can have infinite number of possible values, which disqualify it as an enum type.
+
+### Risks and Mitigations
+
+<!--
+What are the risks of this proposal, and how do we mitigate? Think broadly.
+For example, consider both security and how this will impact the larger
+Kubernetes ecosystem.
+
+How will security be reviewed, and by whom?
+
+How will UX be reviewed, and by whom?
+
+Consider including folks who also work outside the SIG or subproject.
+-->
+
+The syntax proposed in this KEP is different from existing implementation of kube-builder.
+Namely, kube-builder requires possible values in the annotation itself, and is treated
+as a validation.
+```go
+package example
+
+// Alias
+// +kubebuilder:validation:Enum=Lion;Wolf;Dragon
+type Alias string
+```
+The two approaches are compatible, but eventually they will have to be unified.
+However, compatibility with the ecosystem is out of scope of this proposal.
+
+## Design Details
+
+<!--
+This section should contain enough information that the specifics of your
+change are understandable. This may include API specs (though not always
+required) or even code snippets. If there's any ambiguity about HOW your
+proposal will be implemented, this is the place to discuss them.
+-->
+
+### OpenAPI v2 Breakage
+This feature is not targeting OpenAPI v2 because it breaks existing code using
+swagger to generate client or server stub from the spec. Take the following spec as 
+an example.
+
+```yaml
+definitions:
+  Foo:
+    type: object
+    properties:
+      bar:
+        type: string
+        enum: 
+         - A
+         - B
+         - C
+```
+
+The generated Java object looks like
+```java
+public class Foo {
+
+  @JsonAdapter(BarEnum.Adapter.class)
+  public enum BarEnum {
+    A("A"),
+    B("B"),
+    C("C");
+    // ...
+  }
+  private BarEnum bar = null;
+}
+```
+If the `enum` field was not in the definition, the `Bar` field would be a String.
+This breaking change happens to all languages that have built-in enum support,
+including Java, Kotlin, and TypeScript.
+
+### Test Plan
+
+<!--
+**Note:** *Not required until targeted at a release.*
+
+Consider the following in developing a test plan for this enhancement:
+- Will there be e2e and integration tests, in addition to unit tests?
+- How will it be tested in isolation vs with other components?
+
+No need to outline all of the test cases, just the general strategy. Anything
+that would count as tricky in the implementation, and anything particularly
+challenging to test, should be called out.
+
+All code is expected to have adequate tests (eventually with coverage
+expectations). Please adhere to the [Kubernetes testing guidelines][testing-guidelines]
+when drafting this test plan.
+
+[testing-guidelines]: https://git.k8s.io/community/contributors/devel/sig-testing/testing.md
+-->
+
+Testing should focus on `kubernetes/kube-openapi` repository. There will be 
+integration tests against cases with valid and invalid definition of enum types.
+
+In the `kubernetes/kubernetes` repository, as part of OpenAPI v3 test suites,
+there should be integration and e2e tests that validate present of enum fields. 
+
+### Graduation Criteria
+
+#### Alpha
+
+ - Feature implemented behind a feature gate, which shares with the main KEP
+ - Initial tests, both in k/k and k/kube-openapi, are completed and enabled
+
+#### Beta
+
+ - All enums in Kubernetes built-in types have enum tags properly added.
+
+#### Stable
+
+This feature should graduate with OpenAPI v3 after beta.
+
+### Upgrade / Downgrade Strategy
+Enable/disable the OpenAPI v3 feature gate.
+
+### Version Skew Strategy
+An old version can still consume OpenAPI v2. For the conversion from v2 to v3 (see main KEP),
+enum types will not present and thus should cause no issue.
+
+## Production Readiness Review Questionnaire
+
+<!--
+
+Production readiness reviews are intended to ensure that features merging into
+Kubernetes are observable, scalable and supportable; can be safely operated in
+production environments, and can be disabled or rolled back in the event they
+cause increased failures in production. See more in the PRR KEP at
+https://git.k8s.io/enhancements/keps/sig-architecture/1194-prod-readiness.
+
+The production readiness review questionnaire must be completed and approved
+for the KEP to move to `implementable` status and be included in the release.
+
+In some cases, the questions below should also have answers in `kep.yaml`. This
+is to enable automation to verify the presence of the review, and to reduce review
+burden and latency.
+
+The KEP must have a approver from the
+[`prod-readiness-approvers`](http://git.k8s.io/enhancements/OWNERS_ALIASES)
+team. Please reach out on the
+[#prod-readiness](https://kubernetes.slack.com/archives/CPNHUMN74) channel if
+you need any help or guidance.
+-->
+
+### Feature Enablement and Rollback
+
+<!--
+This section must be completed when targeting alpha to a release.
+-->
+
+###### How can this feature be enabled / disabled in a live cluster?
+
+<!--
+Pick one of these and delete the rest.
+-->
+
+- [X] Feature gate (also fill in values in `kep.yaml`)
+  - Feature gate name: `OpenAPIv3Enabled`
+  - Components depending on the feature gate: `kube-apiserver`
+- [ ] Other
+  - Describe the mechanism:
+  - Will enabling / disabling the feature require downtime of the control
+    plane?
+  - Will enabling / disabling the feature require downtime or reprovisioning
+    of a node? (Do not assume `Dynamic Kubelet Config` feature is enabled).
+
+###### Does enabling the feature change any default behavior?
+
+<!--
+Any change of default behavior may be surprising to users or break existing
+automations, so be extremely careful here.
+-->
+
+No. This feature does not affect existing OpenAPI v2 generator. The tag in internal
+APIs would be ignored by existing tooling.
+
+###### Can the feature be disabled once it has been enabled (i.e. can we roll back the enablement)?
+
+<!--
+Describe the consequences on existing workloads (e.g., if this is a runtime
+feature, can it break the existing applications?).
+
+NOTE: Also set `disable-supported` to `true` or `false` in `kep.yaml`.
+-->
+
+Yes. This feature can be turned off with OpenAPI v3.
+###### What happens if we reenable the feature if it was previously rolled back?
+
+This feature needs access only to information immutable at run-time. There should
+be no problem re-enabling it.
+###### Are there any tests for feature enablement/disablement?
+
+<!--
+The e2e framework does not currently support enabling or disabling feature
+gates. However, unit tests in each component dealing with managing data, created
+with and without the feature, are necessary. At the very least, think about
+conversion tests if API types are being modified.
+-->
+N/A
+### Rollout, Upgrade and Rollback Planning
+
+<!--
+This section must be completed when targeting beta to a release.
+-->
+
+###### How can a rollout or rollback fail? Can it impact already running workloads?
+
+<!--
+Try to be as paranoid as possible - e.g., what if some components will restart
+mid-rollout?
+
+Be sure to consider highly-available clusters, where, for example,
+feature flags will be enabled on some API servers and not others during the
+rollout. Similarly, consider large clusters and how enablement/disablement
+will rollout across nodes.
+-->
+
+###### What specific metrics should inform a rollback?
+
+<!--
+What signals should users be paying attention to when the feature is young
+that might indicate a serious problem?
+-->
+
+###### Were upgrade and rollback tested? Was the upgrade->downgrade->upgrade path tested?
+
+<!--
+Describe manual testing that was done and the outcomes.
+Longer term, we may want to require automated upgrade/rollback tests, but we
+are missing a bunch of machinery and tooling and can't do that now.
+-->
+
+###### Is the rollout accompanied by any deprecations and/or removals of features, APIs, fields of API types, flags, etc.?
+
+<!--
+Even if applying deprecation policies, they may still surprise some users.
+-->
+
+### Monitoring Requirements
+
+<!--
+This section must be completed when targeting beta to a release.
+-->
+
+###### How can an operator determine if the feature is in use by workloads?
+
+<!--
+Ideally, this should be a metric. Operations against the Kubernetes API (e.g.,
+checking if there are objects with field X set) may be a last resort. Avoid
+logs or events for this purpose.
+-->
+
+###### How can someone using this feature know that it is working for their instance?
+
+<!--
+For instance, if this is a pod-related feature, it should be possible to determine if the feature is functioning properly
+for each individual pod.
+Pick one more of these and delete the rest.
+Please describe all items visible to end users below with sufficient detail so that they can verify correct enablement
+and operation of this feature.
+Recall that end users cannot usually observe component logs or access metrics.
+-->
+
+- [ ] Events
+  - Event Reason: 
+- [ ] API .status
+  - Condition name: 
+  - Other field: 
+- [ ] Other (treat as last resort)
+  - Details:
+
+###### What are the reasonable SLOs (Service Level Objectives) for the enhancement?
+
+<!--
+This is your opportunity to define what "normal" quality of service looks like
+for a feature.
+
+It's impossible to provide comprehensive guidance, but at the very
+high level (needs more precise definitions) those may be things like:
+  - per-day percentage of API calls finishing with 5XX errors <= 1%
+  - 99% percentile over day of absolute value from (job creation time minus expected
+    job creation time) for cron job <= 10%
+  - 99.9% of /health requests per day finish with 200 code
+
+These goals will help you determine what you need to measure (SLIs) in the next
+question.
+-->
+
+###### What are the SLIs (Service Level Indicators) an operator can use to determine the health of the service?
+
+<!--
+Pick one more of these and delete the rest.
+-->
+
+- [ ] Metrics
+  - Metric name:
+  - [Optional] Aggregation method:
+  - Components exposing the metric:
+- [ ] Other (treat as last resort)
+  - Details:
+
+###### Are there any missing metrics that would be useful to have to improve observability of this feature?
+
+<!--
+Describe the metrics themselves and the reasons why they weren't added (e.g., cost,
+implementation difficulties, etc.).
+-->
+
+### Dependencies
+
+<!--
+This section must be completed when targeting beta to a release.
+-->
+
+###### Does this feature depend on any specific services running in the cluster?
+
+<!--
+Think about both cluster-level services (e.g. metrics-server) as well
+as node-level agents (e.g. specific version of CRI). Focus on external or
+optional services that are needed. For example, if this feature depends on
+a cloud provider API, or upon an external software-defined storage or network
+control plane.
+
+For each of these, fill in the following—thinking about running existing user workloads
+and creating new ones, as well as about cluster-level services (e.g. DNS):
+  - [Dependency name]
+    - Usage description:
+      - Impact of its outage on the feature:
+      - Impact of its degraded performance or high-error rates on the feature:
+-->
+
+### Scalability
+
+<!--
+For alpha, this section is encouraged: reviewers should consider these questions
+and attempt to answer them.
+
+For beta, this section is required: reviewers must answer these questions.
+
+For GA, this section is required: approvers should be able to confirm the
+previous answers based on experience in the field.
+-->
+
+###### Will enabling / using this feature result in any new API calls?
+
+<!--
+Describe them, providing:
+  - API call type (e.g. PATCH pods)
+  - estimated throughput
+  - originating component(s) (e.g. Kubelet, Feature-X-controller)
+Focusing mostly on:
+  - components listing and/or watching resources they didn't before
+  - API calls that may be triggered by changes of some Kubernetes resources
+    (e.g. update of object X triggers new updates of object Y)
+  - periodic API calls to reconcile state (e.g. periodic fetching state,
+    heartbeats, leader election, etc.)
+-->
+
+No. This feature only adds enum fields to enum types.
+###### Will enabling / using this feature result in introducing new API types?
+
+<!--
+Describe them, providing:
+  - API type
+  - Supported number of objects per cluster
+  - Supported number of objects per namespace (for namespace-scoped objects)
+-->
+
+No.
+###### Will enabling / using this feature result in any new calls to the cloud provider?
+
+<!--
+Describe them, providing:
+  - Which API(s):
+  - Estimated increase:
+-->
+No.
+###### Will enabling / using this feature result in increasing size or count of the existing API objects?
+
+<!--
+Describe them, providing:
+  - API type(s):
+  - Estimated increase in size: (e.g., new annotation of size 32B)
+  - Estimated amount of new objects: (e.g., new Object X for every existing Pod)
+-->
+No. Enum information only appears in `/openapi/` endpoints but not standard APIs.
+###### Will enabling / using this feature result in increasing time taken by any operations covered by existing SLIs/SLOs?
+
+<!--
+Look at the [existing SLIs/SLOs].
+
+Think about adding additional work or introducing new steps in between
+(e.g. need to do X to start a container), etc. Please describe the details.
+
+[existing SLIs/SLOs]: https://git.k8s.io/community/sig-scalability/slos/slos.md#kubernetes-slisslos
+-->
+No.
+###### Will enabling / using this feature result in non-negligible increase of resource usage (CPU, RAM, disk, IO, ...) in any components?
+
+<!--
+Things to keep in mind include: additional in-memory state, additional
+non-trivial computations, excessive access to disks (including increased log
+volume), significant amount of data sent and/or received over network, etc.
+This through this both in small and large cases, again with respect to the
+[supported limits].
+
+[supported limits]: https://git.k8s.io/community//sig-scalability/configs-and-limits/thresholds.md
+-->
+No. The addition of enum fields take negligible amount of memory.
+### Troubleshooting
+
+<!--
+This section must be completed when targeting beta to a release.
+
+The Troubleshooting section currently serves the `Playbook` role. We may consider
+splitting it into a dedicated `Playbook` document (potentially with some monitoring
+details). For now, we leave it here.
+-->
+
+###### How does this feature react if the API server and/or etcd is unavailable?
+
+###### What are other known failure modes?
+
+<!--
+For each of them, fill in the following information by copying the below template:
+  - [Failure mode brief description]
+    - Detection: How can it be detected via metrics? Stated another way:
+      how can an operator troubleshoot without logging into a master or worker node?
+    - Mitigations: What can be done to stop the bleeding, especially for already
+      running user workloads?
+    - Diagnostics: What are the useful log messages and their required logging
+      levels that could help debug the issue?
+      Not required until feature graduated to beta.
+    - Testing: Are there any tests for failure mode? If not, describe why.
+-->
+
+###### What steps should be taken if SLOs are not being met to determine the problem?
+
+## Implementation History
+
+<!--
+Major milestones in the lifecycle of a KEP should be tracked in this section.
+Major milestones might include:
+- the `Summary` and `Motivation` sections being merged, signaling SIG acceptance
+- the `Proposal` section being merged, signaling agreement on a proposed design
+- the date implementation started
+- the first Kubernetes release where an initial version of the KEP was available
+- the version of Kubernetes where the KEP graduated to general availability
+- when the KEP was retired or superseded
+-->
+
+## Drawbacks
+
+<!--
+Why should this KEP _not_ be implemented?
+-->
+This KEP will break any users that expect enum types to be plain strings. 
+This is the main reason for not implementing this feature in OpenAPI v2 (see Alternative below).
+## Alternatives
+
+<!--
+What other approaches did you consider, and why did you rule them out? These do
+not need to be as detailed as the proposal, but should include enough
+information to express the idea and why it was not acceptable.
+-->
+
+### Directly into OpenAPI v2
+
+The original design is to make the changes independent of OpenAPI v3. Doing this will
+cause swagger-generated type to switch from plain string to a built-in enum, provided
+the language supports enum type. This will break client code for many popular languages. 
+We can use a feature gate to give the maintainer some time to adapt the change,
+but eventually the breakage will happen.
diff --git a/keps/sig-api-machinery/2887-openapi-enum-types/kep.yaml b/keps/sig-api-machinery/2887-openapi-enum-types/kep.yaml
new file mode 100644
index 000000000000..962e3ad9abd5
--- /dev/null
+++ b/keps/sig-api-machinery/2887-openapi-enum-types/kep.yaml
@@ -0,0 +1,40 @@
+title: KEP Template
+kep-number: 2887
+authors:
+  - "@jiahuif"
+owning-sig: sig-api-machinery
+participating-sigs: []
+status: implementable
+creation-date: 2021-08-20
+reviewers:
+  - '@jpbetz'
+  - '@apelisse'
+approvers:
+  - '@jpbetz'
+
+see-also:
+  - https://github.com/kubernetes/enhancements/issues/2896
+replaces: []
+
+# The target maturity stage in the current dev cycle for this KEP.
+stage: alpha
+
+# The most recent milestone for which work toward delivery of this KEP has been
+# done. This can be the current (upcoming) milestone, if it is being actively
+# worked on.
+latest-milestone: "v1.23"
+
+# The milestone at which this feature was, or is targeted to be, at each stage.
+milestone:
+  alpha: "v1.23"
+
+# The following PRR answers are required at alpha release
+# List the feature gate name and the components for which it must be enabled
+feature-gates:
+  - name: OpenAPIv3Enabled # inherited from the main KEP, #2896
+    components:
+      - kube-apiserver
+disable-supported: true
+
+# The following PRR answers are required at beta release
+metrics: [] #TBD