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fix: Support form and url fields in Elicitation capability per 2025-11-25 spec (#731)

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Update the ClientCapabilities.Elicitation record to accept optional "form"
and "url" fields as defined in the MCP 2025-11-25 specification.

Previously, deserializing an InitializeRequest with
`{"capabilities":{"elicitation":{"form":{}}}}` would fail with
UnrecognizedPropertyException because the Elicitation record was empty.

Changes:
- Add nested Form and Url marker records to Elicitation
- Add no-arg constructor for backward compatibility (serializes to {})
- Add elicitation(boolean form, boolean url) builder method
- Add comprehensive tests for deserialization and serialization

Fixes #724
This commit is contained in:
Rohit 2026-01-08 10:29:39 -08:00 • committed by GitHub
commit e7901da010
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57
mcp-core/src/main/java/io/modelcontextprotocol/spec/McpSchema.java
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@ -416,9 +416,47 @@ public final class McpSchema {
* maintain control over user interactions and data sharing while enabling servers
* to gather necessary information dynamically. Servers can request structured
* data from users with optional JSON schemas to validate responses.
*
* <p>
* Per the 2025-11-25 spec, clients can declare support for specific elicitation
* modes:
* <ul>
* <li>{@code form} - In-band structured data collection with optional schema
* validation</li>
* <li>{@code url} - Out-of-band interaction via URL navigation</li>
* </ul>
*
* <p>
* For backward compatibility, an empty elicitation object {@code {}} is
* equivalent to declaring support for form mode only.
*
* @param form support for in-band form-based elicitation
* @param url support for out-of-band URL-based elicitation
*/
@JsonInclude(JsonInclude.Include.NON_ABSENT)
public record Elicitation() {
public record Elicitation(@JsonProperty("form") Form form, @JsonProperty("url") Url url) {
/**
* Marker record indicating support for form-based elicitation mode.
*/
@JsonInclude(JsonInclude.Include.NON_ABSENT)
public record Form() {
}
/**
* Marker record indicating support for URL-based elicitation mode.
*/
@JsonInclude(JsonInclude.Include.NON_ABSENT)
public record Url() {
}
/**
* Creates an Elicitation with default settings (backward compatible, produces
* empty JSON object).
*/
public Elicitation() {
this(null, null);
}
}
public static Builder builder() {
@ -450,11 +488,28 @@ public final class McpSchema {
return this;
}
/**
* Enables elicitation capability with default settings (backward compatible,
* produces empty JSON object).
* @return this builder
*/
public Builder elicitation() {
this.elicitation = new Elicitation();
return this;
}
/**
* Enables elicitation capability with explicit form and/or url mode support.
* @param form whether to support form-based elicitation
* @param url whether to support URL-based elicitation
* @return this builder
*/
public Builder elicitation(boolean form, boolean url) {
this.elicitation = new Elicitation(form ? new Elicitation.Form() : null,
url ? new Elicitation.Url() : null);
return this;
}
public ClientCapabilities build() {
return new ClientCapabilities(experimental, roots, sampling, elicitation);
}