Schema Validator
The extension provides integration with the Vert.x JSON Schema library.
When present, all client requests and notifications are validated against the relevant MCP JSON schema.
Validation errors are transformed into protocol error messages with the JSON-RPC error code -32600 (INVALID_REQUEST).
The error message includes the name of the schema type that failed validation, e.g. Schema validation failed - CallToolRequest: ….
If you want to use the Schema Validator in your application you’ll need to add the io.quarkiverse.mcp:quarkus-mcp-server-schema-validator extension to your build file first.
For instance, with Maven, add the following dependency to your POM file:
<dependency>
<groupId>io.quarkiverse.mcp</groupId>
<artifactId>quarkus-mcp-server-schema-validator</artifactId>
<version>${quarkus-mcp.version}</version>
</dependency>No further configuration is needed. Validations are performed automatically.
The extension includes MCP JSON schemas for the following protocol versions: 2024-11-05, 2025-03-26, 2025-06-18, and 2025-11-25.
The appropriate schema is selected based on the protocol version negotiated during the client initialization.
| The MCP server performs some basic validation of messages by default. However, this extension ensures that message instances are valid, as defined by the JSON Schema specification. |