langchain4j spring-ai mcp integration doesn't respect valid schema and wants parameters to be specified #490
Description
Spring AI MCP server tools is not exporting parameters as such
{
"tools":[
{
"name":"get-weather",
"description":"Function to get the weather forecast for a given city",
"inputSchema":{
"type":"object",
"properties":{
"city":{
"type":"string",
"description":"The city to get the weather forecast for"
}
},
"required":[
"city"
],
"additionalProperties":false
}
}
]
}
Definition of tool in spring AI (1.1.0-M3 latest one)
@Service
public static class WeatherToolService {
@Tool(name = "get-weather", description = "Function to get the weather forecast for a given city")
public static Map<String, Object> getWeather(@ToolParam(required = true, description = "The city to get the weather forecast for") String city) {
return Map.of(
"city", city,
"forecast", "a beautiful and sunny weather",
"temperature", "from 10°C in the morning up to 24°C in the afternoon");
}
}
Export function
@Configuration
@EnableAutoConfiguration
public static class SpringAiMSPServerContext {
@Bean
public WeatherToolService weatherToolService() {
return new WeatherToolService();
}
@Bean
public WebFluxSseServerTransportProvider sseServerTransportProvider(ObjectMapper mapper) {
return WebFluxSseServerTransportProvider.builder()
.jsonMapper(new JacksonMcpJsonMapper(mapper))
.messageEndpoint("/mcp/message")
.build();
}
@Bean
public RouterFunction<?> mcpRouterFunction(WebFluxSseServerTransportProvider transportProvider) {
return transportProvider.getRouterFunction();
}
@Bean
public McpSyncServer mcpServer(McpServerTransportProvider transportProvider, WeatherToolService tool) {
var capabilities = McpSchema.ServerCapabilities.builder().tools(true).logging().build();
return McpServer
.sync(transportProvider)
.serverInfo("MCP Server", "1.0.0")
.capabilities(capabilities)
.tools(McpToolUtils.toSyncToolSpecifications(ToolCallbacks.from(tool)))
.build();
}
}
finally the code fails in LangChain4j (Tool lacking parameters)
private List<ToolSpecification> toToolSpecifications(LlmRequest llmRequest) {
List<ToolSpecification> toolSpecifications = new ArrayList<>();
llmRequest
.tools()
.values()
.forEach(
baseTool -> {
if (baseTool.declaration().isPresent()) {
FunctionDeclaration functionDeclaration = baseTool.declaration().get();
if (functionDeclaration.parameters().isPresent()) {
Schema schema = functionDeclaration.parameters().get();
ToolSpecification toolSpecification =
ToolSpecification.builder()
.name(baseTool.name())
.description(baseTool.description())
.parameters(toParameters(schema))
.build();
toolSpecifications.add(toolSpecification);
} else {
// TODO exception or something else?
throw new IllegalStateException("Tool lacking parameters: " + baseTool);
}
} else {
// TODO exception or something else?
throw new IllegalStateException("Tool lacking declaration: " + baseTool);
}
});
return toolSpecifications;
}