Add support for elicitation #138
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Pull Request Overview
Adds initial support for the new “elicitation” feature in the MCP protocol, including data types, capability checks, client/server handling, and basic tests.
- Introduces
CreateElicitationRequestandCreateElicitationResulttypes and updatesMethod.Defined - Adds client/server capability checks and a
Server.createElicitationhelper - Adds two new tests in
ClientTestfor reject and success paths
Reviewed Changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| src/jvmTest/kotlin/client/ClientTest.kt | New tests for server-initiated elicitation accept/reject paths |
| src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types.kt | Added elicitation types and client capability field |
| src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/server/Server.kt | Added createElicitation and server-side capability assertion |
| src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/Client.kt | Added client-side capability assertion for elicitation requests |
| api/kotlin-sdk.api | Updated public API signature dump to include elicitation types |
Comments suppressed due to low confidence (1)
src/jvmTest/kotlin/client/ClientTest.kt:846
- [nitpick] Consider adding tests for the
declineandcancelbranches ofCreateElicitationResult.Actionto ensure all response paths are handled correctly.
fun `should handle server elicitation`() = runTest {
| Method.Defined.ElicitationCreate -> { | ||
| if (capabilities.elicitation == null) { | ||
| throw IllegalStateException( | ||
| "Client does not support elicitation capability (required for $method)" |
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The exception message is inconsistent with the server-side text and the test expectation. Consider matching it to "Client does not support elicitation (required for elicitation/create)" and use method.value rather than $method for clarity.
Suggested change
| "Client does not support elicitation capability (required for $method)" | |
| "Client does not support elicitation (required for elicitation/create)" |
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devcrocod
previously approved these changes
Jul 9, 2025
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Your PR looks very great!
I was not sure whether to add the tests to ClientTest or ServerTest. (It seems to me that the tests should be divided by feature and not by client/server side, as most features involve both client and server, but I respected how it is done today.)
You did right. This separation will actually be helpful later on when I split sdk into server and client modules. At that point, might also revisit the tests. Additionally, we have an open issue for adding integration tests.
I was not sure whether to add a method to Client to register an elicitation handler (i.e. wrap the setRequestHandler(...) call). Please advise me on what you think is best. (If that is best to add a wrapper method, maybe this can be implemented as a follow-up?)
I think adding a dedicated method for elicitation would be a good idea. It’s not critical for this PR, but if you include it here, that would be great.
The CreateElicitationRequest.RequestedSchema class I introduced is duplicated from Tool.Input. Maybe that should be factored-out in a JsonSchema top-level class in types.kt. I was not sure you would approve that, so I did not factor it out. Please tell me if you'd prefer I factor that out. (The support for the new Tool output schema in the latest protocol version will also need the same type.)
For now, your approach looks like a good solution. I’m not sure how the spec will evolve, and having separate classes might actually help us adapt to future changes more easily. Even if it means some duplication for the time being. I think you can leave it as it is for now and consider refactoring it in a separate PR
|
@devcrocod Thanks a lot for your review.
OK, I can add that in this PR. Would an fun Client.setElicitationHandler(handler: (CreateElicitationRequest) -> CreateElicitationResult) { /* ... */ }
That makes sense! |
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Added the new method and rebased on main. |
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| Package | Type | Package file | Manager | Update | Change | |---|---|---|---|---|---| | [io.modelcontextprotocol:kotlin-sdk](https://github.com/modelcontextprotocol/kotlin-sdk) | dependencies | misk/gradle/libs.versions.toml | gradle | minor | `0.5.0` -> `0.6.0` | | [org.jetbrains.kotlinx:kotlinx-serialization-json](https://github.com/Kotlin/kotlinx.serialization) | dependencies | misk/gradle/libs.versions.toml | gradle | minor | `1.7.3` -> `1.9.0` | | [org.jetbrains.kotlinx:kotlinx-serialization-core](https://github.com/Kotlin/kotlinx.serialization) | dependencies | misk/gradle/libs.versions.toml | gradle | minor | `1.7.3` -> `1.9.0` | | [com.google.apis:google-api-services-storage](http://nexus.sonatype.org/oss-repository-hosting.html) ([source](http://svn.sonatype.org/spice/tags/oss-parent-7)) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `v1-rev20250718-2.0.0` -> `v1-rev20250814-2.0.0` | | [software.amazon.awssdk:sdk-core](https://aws.amazon.com/sdkforjava) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `2.32.23` -> `2.32.24` | | [software.amazon.awssdk:sqs](https://aws.amazon.com/sdkforjava) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `2.32.23` -> `2.32.24` | | [software.amazon.awssdk:regions](https://aws.amazon.com/sdkforjava) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `2.32.23` -> `2.32.24` | | [software.amazon.awssdk:dynamodb-enhanced](https://aws.amazon.com/sdkforjava) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `2.32.23` -> `2.32.24` | | [software.amazon.awssdk:dynamodb](https://aws.amazon.com/sdkforjava) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `2.32.23` -> `2.32.24` | | [software.amazon.awssdk:aws-core](https://aws.amazon.com/sdkforjava) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `2.32.23` -> `2.32.24` | | [software.amazon.awssdk:bom](https://aws.amazon.com/sdkforjava) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `2.32.23` -> `2.32.24` | | [software.amazon.awssdk:auth](https://aws.amazon.com/sdkforjava) | dependencies | misk/gradle/libs.versions.toml | gradle | patch | `2.32.23` -> `2.32.24` | --- ### Release Notes <details> <summary>modelcontextprotocol/kotlin-sdk (io.modelcontextprotocol:kotlin-sdk)</summary> ### [`v0.6.0`](https://github.com/modelcontextprotocol/kotlin-sdk/releases/tag/0.6.0) [Compare Source](modelcontextprotocol/kotlin-sdk@0.5.0...0.6.0) #### What's Changed - Update jreleaser to fix publication issue by [@​e5l](https://github.com/e5l) in modelcontextprotocol/kotlin-sdk#91 - Disable configuration cache to fix jreleaser issue by [@​e5l](https://github.com/e5l) in modelcontextprotocol/kotlin-sdk#92 - feat: Add audio type according to 2025-03-26 spec by [@​SeanChinJunKai](https://github.com/SeanChinJunKai) in modelcontextprotocol/kotlin-sdk#68 - fix(client): serialize inputSchema as input\_schema by [@​shiqicao](https://github.com/shiqicao) in modelcontextprotocol/kotlin-sdk#97 - fix(client) add encodeDefault for field with non spec default value by [@​shiqicao](https://github.com/shiqicao) in modelcontextprotocol/kotlin-sdk#99 - Make McpJson public to allow flexible protocol development by [@​parnurzeal](https://github.com/parnurzeal) in modelcontextprotocol/kotlin-sdk#103 - fix: apply `requestBuilder` headers when sending rpc messages by [@​dead8309](https://github.com/dead8309) in modelcontextprotocol/kotlin-sdk#96 - fix: Remove [@​SerialName](https://github.com/SerialName) annotation for inputSchema by [@​adamglin0](https://github.com/adamglin0) in modelcontextprotocol/kotlin-sdk#105 - add ios and wasm targets by [@​devcrocod](https://github.com/devcrocod) in modelcontextprotocol/kotlin-sdk#81 - Add dependabot by [@​StefMa](https://github.com/StefMa) in modelcontextprotocol/kotlin-sdk#121 - Bump org.jetbrains.kotlinx:kotlinx-serialization-json from 1.7.3 to 1.8.1 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#127 - Bump io.github.oshai:kotlin-logging from 7.0.0 to 7.0.7 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#126 - Bump org.jetbrains.kotlinx.binary-compatibility-validator from 0.17.0 to 0.18.0 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#125 - update kotlin to 2.2.0 and ktor to 3.1.3 by [@​devcrocod](https://github.com/devcrocod) in modelcontextprotocol/kotlin-sdk#120 - Add client roots addition/removal API and listRoots handler by [@​ptitjes](https://github.com/ptitjes) in modelcontextprotocol/kotlin-sdk#118 - Bump org.slf4j:slf4j-simple from 2.0.16 to 2.0.17 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#131 - Bump org.jetbrains.kotlinx:kotlinx-serialization-json from 1.8.1 to 1.9.0 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#132 - Bump io.mockk:mockk from 1.13.13 to 1.14.4 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#133 - Remove fixed suffix /sse by [@​adamglin0](https://github.com/adamglin0) in modelcontextprotocol/kotlin-sdk#108 - sse server does not process endpoint correctly when sse path is not a directory by [@​shendaxia-sm](https://github.com/shendaxia-sm) in modelcontextprotocol/kotlin-sdk#43 - Add labels to dependabot configuration for Kotlin and GitHub Actions by [@​devcrocod](https://github.com/devcrocod) in modelcontextprotocol/kotlin-sdk#135 - feat: add tool annotations according to 2025-03-26 spec by [@​SeanChinJunKai](https://github.com/SeanChinJunKai) in modelcontextprotocol/kotlin-sdk#71 - Bump ktor from 3.1.3 to 3.2.1 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#140 - Bump gradle/actions from 4.0.0 to 4.4.1 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#122 - Bump org.jreleaser from 1.17.0 to 1.19.0 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#141 - refactor `SseClientTransport` by [@​devcrocod](https://github.com/devcrocod) in modelcontextprotocol/kotlin-sdk#142 - atomic and persistent collections for thread safety by [@​devcrocod](https://github.com/devcrocod) in modelcontextprotocol/kotlin-sdk#143 - Bump org.gradle.toolchains.foojay-resolver-convention from 0.8.0 to 1.0.0 by [@​dependabot](https://github.com/dependabot)\[bot] in modelcontextprotocol/kotlin-sdk#130 - Add support for elicitation by [@​ptitjes](https://github.com/ptitjes) in modelcontextprotocol/kotlin-sdk#138 - Add support for tool structured content and output schema by [@​ptitjes](https://github.com/ptitjes) in modelcontextprotocol/kotlin-sdk#146 - Add streamable http client transport by [@​devcrocod](https://github.com/devcrocod) in modelcontextprotocol/kotlin-sdk#147 - Refactor JSON processing to exclude "method" in serialization by [@​devcrocod](https://github.com/devcrocod) in [#​157](modelcontextprotocol/kotlin-sdk#157) - Release 0.6.0 by [@​devcrocod](https://github.com/devcrocod) in modelcontextprotocol/kotlin-sdk#149 #### New Contributors - [@​shiqicao](https://github.com/shiqicao) made their first contribution in modelcontextprotocol/kotlin-sdk#97 - [@​parnurzeal](https://github.com/parnurzeal) made their first contribution in modelcontextprotocol/kotlin-sdk#103 - [@​dead8309](https://github.com/dead8309) made their first contribution in modelcontextprotocol/kotlin-sdk#96 - [@​adamglin0](https://github.com/adamglin0) made their first contribution in modelcontextprotocol/kotlin-sdk#105 - [@​StefMa](https://github.com/StefMa) made their first contribution in modelcontextprotocol/kotlin-sdk#121 - [@​dependabot](https://github.com/dependabot)\[bot] made their first contribution in modelcontextprotocol/kotlin-sdk#127 - [@​ptitjes](https://github.com/ptitjes) made their first contribution in modelcontextprotocol/kotlin-sdk#118 - [@​shendaxia-sm](https://github.com/shendaxia-sm) made their first contribution in modelcontextprotocol/kotlin-sdk#43 **Full Changelog**: modelcontextprotocol/kotlin-sdk@0.5.0...0.6.0 </details> <details> <summary>Kotlin/kotlinx.serialization (org.jetbrains.kotlinx:kotlinx-serialization-json)</summary> ### [`v1.9.0`](https://github.com/Kotlin/kotlinx.serialization/blob/HEAD/CHANGELOG.md#190--2025-06-27) \================== This release updates Kotlin version to 2.2.0, includes several bugfixes and provides serializers for kotlin.time.Instant. #### Add kotlin.time.Instant serializers Instant class was moved from kotlinx-datetime library to Kotlin standard library. As a result, kotlinx-datetime 0.7.0 no longer has serializers for the Instant class. To use new kotlin.time.Instant class in your [@​Serializable](https://github.com/Serializable) classes, you can use this 1.9.0 kotlinx-serialization version (Kotlin 2.2 is required). You can choose between default `InstantSerializer` which uses its string representation, or specify `InstantComponentSerializer` that represents instant as its components. See details in the [PR](Kotlin/kotlinx.serialization#2945). #### Other bugfixes - Fix resize in JsonPath ([#​2995](Kotlin/kotlinx.serialization#2995)) - Fixed proguard rules for obfuscation to work correctly ([#​2983](Kotlin/kotlinx.serialization#2983)) ### [`v1.8.1`](https://github.com/Kotlin/kotlinx.serialization/blob/HEAD/CHANGELOG.md#181--2025-03-31) \================== This release updates Kotlin version to 2.1.20, while also providing several important improvements and bugfixes. #### Improvements - Implemented encoding null in key and value of a map in Protobuf ([#​2910](Kotlin/kotlinx.serialization#2910)) - Make type argument in JsonTransformingSerializer nullable ([#​2911](Kotlin/kotlinx.serialization#2911)) - Use SPDX identifier in POMs ([#​2936](Kotlin/kotlinx.serialization#2936)) (thanks to [Leon Linhart](https://github.com/TheMrMilchmann)) - Add watchosDeviceArm64 to Okio integration module ([#​2920](Kotlin/kotlinx.serialization#2920)) (thanks to [Daniel Santiago](https://github.com/danysantiago)) - Update kotlinx-io version to 0.6.0 ([#​2933](Kotlin/kotlinx.serialization#2933)) (thanks to [Piotr Krzemiński](https://github.com/krzema12)) #### Bugfixes - Fix incorrect enum coercion during deserialization from JsonElement ([#​2962](Kotlin/kotlinx.serialization#2962)) - Supply proper equals(), hashCode(), and toString() for SerialDescriptor() wrapper ([#​2942](Kotlin/kotlinx.serialization#2942)) - Do not encode empty packed collections in protobuf ([#​2907](Kotlin/kotlinx.serialization#2907)) ### [`v1.8.0`](https://github.com/Kotlin/kotlinx.serialization/blob/HEAD/CHANGELOG.md#180--2025-01-06) \================== This release contains all of the changes from 1.8.0-RC. Kotlin 2.1.0 is used as a default, while upcoming 2.1.10 is also supported. Also added small bugfixes, including speedup of ProtoWireType.from ([#​2879](Kotlin/kotlinx.serialization#2879)). </details> --- ### Configuration 📅 **Schedule**: Branch creation - "after 6pm every weekday,before 2am every weekday" in timezone Australia/Melbourne, Automerge - At any time (no schedule defined). 🚦 **Automerge**: Enabled. ♻ **Rebasing**: Never, or you tick the rebase/retry checkbox. 👻 **Immortal**: This PR will be recreated if closed unmerged. Get [config help](https://github.com/renovatebot/renovate/discussions) if that's undesired. --- - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate). GitOrigin-RevId: 40e2f07ecd958e92e64c571d1351e91f96e71ce7
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Fixes #137
In this PR, I add:
ClientTestMotivation and Context
To support the new elicitation feature of the 2025-06-18 protocol version.
How Has This Been Tested?
I added two tests in
ClientTest. The tests are not extensive yet as I only check:Maybe should I add some more tests? Please advise me.
Breaking Changes
N/A
Types of changes
Checklist
Additional context
I was not sure whether to add the tests to
ClientTestorServerTest. (It seems to me that the tests should be divided by feature and not by client/server side, as most features involve both client and server, but I respected how it is done today.)I was not sure whether to add a method to
Clientto register an elicitation handler (i.e. wrap thesetRequestHandler(...)call). Please advise me on what you think is best. (If that is best to add a wrapper method, maybe this can be implemented as a follow-up?)The
CreateElicitationRequest.RequestedSchemaclass I introduced is duplicated fromTool.Input. Maybe that should be factored-out in aJsonSchematop-level class intypes.kt. I was not sure you would approve that, so I did not factor it out. Please tell me if you'd prefer I factor that out. (The support for the new Tool output schema in the latest protocol version will also need the same type.)