apache/shenyu · error · IllegalArgumentException

OpenAPI methodType cannot be null or empty

Error message

OpenAPI methodType cannot be null or empty

What it means

McpServiceEventListener.validateClientConfig also requires the ShenyuMcpTool's method (HTTP methodType, e.g. GET/POST) to be non-blank. When blank it logs a hint about OpenApiConfig and throws IllegalArgumentException, preventing registration of a tool with no HTTP method.

Solutions

1. Set methodType (GET/POST/etc.) on the OpenApiConfig of each @ShenyuMcpTool
2. Validate tool DTOs before registration to catch blanks early
3. Check logs for 'OpenAPI methodType is null or empty' to find the offending tool
4. Regenerate tool definitions from the OpenAPI spec preserving operation methods

Example fix

// before
@OpenApiConfig(pathKey = "/weather")
// after
@OpenApiConfig(pathKey = "/weather", methodType = "GET")

if (tool.getOpenApiConfig() == null || StringUtils.isBlank(tool.getOpenApiConfig().getMethodType())) {
    throw new IllegalStateException("@ShenyuMcpTool " + tool.getName() + " missing OpenApiConfig methodType");
}

try { listener.buildMcpToolsRegisterDTO(tool); }
catch (IllegalArgumentException e) {
    log.error("MCP tool config invalid: {}", e.getMessage());
}

When it happens

Trigger: Building MCP tools register DTOs when the @ShenyuMcpTool's OpenApiConfig methodType is null or empty while pathKey is valid.

Common situations: Tool configs hand-written without methodType; spec conversion dropping the http method; annotation attributes left at defaults that resolve to empty.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

• OpenAPI pathKey cannot be null or empty
• OpenAPI document is missing the top-level 'servers' field…
• Unsupported Swagger version, only Swagger 2.0 and OpenAPI…
• client register param must config the appName or contextPath
• The configuration shenyu.discovery.serverList in xml/yml…

AI-assisted analysis of apache/shenyu@567142e072 (2026-09-12). Data as JSON: /api/errors/1b852c11d2dada4e. Report an issue: GitHub.

Appendix: source

Thrown at shenyu-client/shenyu-client-mcp/shenyu-client-mcp-register/src/main/java/org/apache/shenyu/client/mcp/McpServiceEventListener.java:383

                                                         final String url, final String namespaceId) {
        validateClientConfig(shenyuMcpTool, url);
        JsonObject openApiJson = McpOpenApiGenerator.generateOpenApiJson(classShenyuClient, shenyuMcpTool, url);
        McpToolsRegisterDTO mcpToolsRegisterDTO = McpToolsRegisterDTOGenerator.generateRegisterDTO(shenyuMcpTool, openApiJson, url, namespaceId);
        MetaDataRegisterDTO metaDataRegisterDTO = buildMetaDataDTO(bean, classShenyuClient, url, clazz, method, namespaceId);
        metaDataRegisterDTO.setEnabled(shenyuMcpTool.getEnable());
        mcpToolsRegisterDTO.setMetaDataRegisterDTO(metaDataRegisterDTO);
        return mcpToolsRegisterDTO;
    }

    private void validateClientConfig(final org.apache.shenyu.client.mcp.common.dto.ShenyuMcpTool methodShenyuClient, final String url) {
        if (StringUtils.isBlank(url)) {
            log.error("OpenAPI pathKey is null or empty, please check OpenApiConfig");
            throw new IllegalArgumentException("OpenAPI pathKey cannot be null or empty");
        }

        if (StringUtils.isBlank(methodShenyuClient.getMethod())) {
            log.error("OpenAPI methodType is null or empty, please check OpenApiConfig");
            throw new IllegalArgumentException("OpenAPI methodType cannot be null or empty");
        }
    }

}

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