Missing `@JsonIgnoreProperties(ignoreUnknown = true)` on capability sub-records

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#766 创建于 2026年1月29日 4 条评论 0 个 reaction 已指派 0 人在 GitHub 查看

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评估

难度: 2/5
预计耗时: 1-3 小时
新手友好度: 55/100

Issue 类型: 缺陷
描述清晰度: 描述清楚
活跃度: 停滞
技术栈: java
领域: api

调研方向

从 mcp-core/src/main/java/io/modelcontextprotocol/spec/McpSchema.java 开始，检查列出的 capability record，并将其与 ClientCapabilities 和 ServerCapabilities 进行比较。完成标准是：在反序列化期间，忽略每个受影响的 capability 子记录中的未知字段，包括嵌套的 elicitation record。

由索引模型根据 Issue 内容生成。

描述

bug P1

Bug description

The top-level ClientCapabilities and ServerCapabilities records have @JsonIgnoreProperties(ignoreUnknown = true), but their nested sub-records do not. Since the ObjectMapper is constructed with default settings (FAIL_ON_UNKNOWN_PROPERTIES = true), any unknown field on a capability sub-object causes a deserialization failure.

This already caused a real breakage when the elicitation capability gained form and url fields (#724, fixed in #731), but the systemic issue remains — the next spec addition to any capability sub-object will break older SDK versions again.

Affected records

In McpSchema.java:

Record	Line	Has annotation?
`ClientCapabilities`	383	Yes
`RootCapabilities`	397	Yes
`Sampling`	410	No
`Elicitation`	437	No
`Elicitation.Form`	443	No
`Elicitation.Url`	450	No
`ServerCapabilities`	535	Yes
`CompletionCapabilities`	548	No
`LoggingCapabilities`	555	No
`PromptCapabilities`	565	No
`ResourceCapabilities`	576	No
`ToolCapabilities`	587	No

Spec reference

The spec schema explicitly states capabilities are not a closed set:

"Known capabilities are defined here, in this schema, but this is not a closed set: any client can define its own, additional capabilities."

ClientCapabilities in schema.json — additionalProperties: false is never set on any capability object or sub-object. Several sub-capabilities (sampling, elicitation, completions, logging) explicitly set additionalProperties: true.

Expected behavior

Unknown fields on capability sub-objects should be silently ignored, matching the behavior of the top-level ClientCapabilities and ServerCapabilities records.

#734 — reports the same issue for ToolCapabilities specifically
#724 / #731 — the elicitation breakage that was fixed by adding fields, not by adding the annotation

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