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…hema (SEP-1613) MCP embeds JSON Schema documents in three places — Tool.inputSchema, Tool.outputSchema, and ElicitRequest.requestedSchema — and SEP-1613 mandates that these documents conform to JSON Schema 2020-12 by default. Servers now reject malformed schemas at both build time (McpServer.build()) and runtime (McpAsyncServer/McpStatelessAsyncServer.addTool()), returning an IllegalArgumentException that identifies the offending field and references SEP-1613. Elicitation requests whose requestedSchema violates the meta-schema are rejected before being sent to the client. Schemas that explicitly declare a different dialect via $schema are accepted without meta-schema validation, since 2020-12 is the default, not the only permitted dialect. Resolves #700 Signed-off-by: Dariusz Jędrzejczyk <2554306+chemicL@users.noreply.github.com>
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LGTM! |
Signed-off-by: Dariusz Jędrzejczyk <2554306+chemicL@users.noreply.github.com>
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Integrates upstream changes through modelcontextprotocol#949 (SEP-1613 JSON Schema 2020-12 meta-schema validation) and addresses reviewer feedback on PR modelcontextprotocol#912. Review feedback addressed ------------------------- - Append icons between annotations and _meta in Resource, ResourceTemplate, Prompt, and Tool, preserving the _meta-always-last convention used throughout the schema (Case A Rule 1). - Icon: switch compact constructor guard from Assert.hasText to Assert.notNull and add @JsonCreator fromJson lenient factory that defaults missing 'src' to '' with a WARN log (Case B Rules 1-2). Prevents deserialization crashes on malformed peer messages. - Icon: remove newly-introduced convenience constructors Icon(src, mimeType) and Icon(src, mimeType, sizes); callers use the Builder. - Implementation: add description, icons, websiteUrl at the end of the component list; add required-first builder(name, version) with builder methods for all new optional fields (Case A Rule 9, Case B Rule 3). - Javadoc: add @param icons to Implementation, Resource, ResourceTemplate, Prompt, and Tool. Tests ----- - Add unknown-field tolerance tests for Icon, Implementation, Resource, ResourceTemplate, Prompt, Tool (Case A Rule 8). - Add null-src, missing-src-deserialization, and lenient-default tests for Icon. - Add backward-compatibility test for the pre-existing 2-arg Implementation constructor. Closes modelcontextprotocol#694
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MCP embeds JSON Schema documents in three places — Tool.inputSchema, Tool.outputSchema, and ElicitRequest.requestedSchema — and SEP-1613 mandates that these documents conform to JSON Schema 2020-12 by default.
Motivation and Context
Servers now reject malformed schemas at both build time (McpServer.build()) and runtime (McpAsyncServer/McpStatelessAsyncServer.addTool()), returning an IllegalArgumentException that identifies the offending field and references SEP-1613. Elicitation requests whose requestedSchema violates the meta-schema are rejected before being sent to the client.
Schemas that explicitly declare a different dialect via $schema are accepted without meta-schema validation, since 2020-12 is the default, not the only permitted dialect.
How Has This Been Tested?
New tests were added.
Breaking Changes
This is a behaviour change required by the 2025-11-25 MCP Specification.
Types of changes
Checklist