The value of "additionalProperties" MUST be a valid JSON Schema.

[lp2jx0309]

The value of "additionalProperties" MUST be a valid JSON Schema.
This keyword has always been a schema in the spec.
https://json-schema.org/draft-07/draft-handrews-json-schema-validation-01#rfc.section.6.5.6
https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-01#name-additionalproperties

[tzolov]

@lp2jx0309, please elaborate.
the JsonSchema has additionalProperties filed:

java-sdk/mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

Line 1206 in 110a8d1

@JsonProperty("additionalProperties") Boolean additionalProperties,