feat(HTTP Request Tool Node): Use DynamicStructuredTool with models supporting it (no-changelog) (#10246)

packages/@n8n/nodes-langchain/utils/N8nTool.ts

@@ -0,0 +1,113 @@
+import type { DynamicStructuredToolInput } from '@langchain/core/tools';
+import { DynamicStructuredTool, DynamicTool } from '@langchain/core/tools';
+import type { IExecuteFunctions, IDataObject } from 'n8n-workflow';
+import { NodeConnectionType, jsonParse, NodeOperationError } from 'n8n-workflow';
+import { StructuredOutputParser } from 'langchain/output_parsers';
+import type { ZodTypeAny } from 'zod';
+import { ZodBoolean, ZodNullable, ZodNumber, ZodObject, ZodOptional } from 'zod';
+
+const getSimplifiedType = (schema: ZodTypeAny) => {
+	if (schema instanceof ZodObject) {
+		return 'object';
+	} else if (schema instanceof ZodNumber) {
+		return 'number';
+	} else if (schema instanceof ZodBoolean) {
+		return 'boolean';
+	} else if (schema instanceof ZodNullable || schema instanceof ZodOptional) {
+		return getSimplifiedType(schema.unwrap());
+	}
+
+	return 'string';
+};
+
+const getParametersDescription = (parameters: Array<[string, ZodTypeAny]>) =>
+	parameters
+		.map(
+			([name, schema]) =>
+				`${name}: (description: ${schema.description ?? ''}, type: ${getSimplifiedType(schema)}, required: ${!schema.isOptional()})`,
+		)
+		.join(',\n ');
+
+export const prepareFallbackToolDescription = (toolDescription: string, schema: ZodObject<any>) => {
+	let description = `${toolDescription}`;
+
+	const toolParameters = Object.entries<ZodTypeAny>(schema.shape);
+
+	if (toolParameters.length) {
+		description += `
+Tool expects valid stringified JSON object with ${toolParameters.length} properties.
+Property names with description, type and required status:
+${getParametersDescription(toolParameters)}
+ALL parameters marked as required must be provided`;
+	}
+
+	return description;
+};
+
+export class N8nTool extends DynamicStructuredTool {
+	private context: IExecuteFunctions;
+
+	constructor(context: IExecuteFunctions, fields: DynamicStructuredToolInput) {
+		super(fields);
+
+		this.context = context;
+	}
+
+	asDynamicTool(): DynamicTool {
+		const { name, func, schema, context, description } = this;
+
+		const parser = new StructuredOutputParser(schema);
+
+		const wrappedFunc = async function (query: string) {
+			let parsedQuery: object;
+
+			// First we try to parse the query using the structured parser (Zod schema)
+			try {
+				parsedQuery = await parser.parse(query);
+			} catch (e) {
+				// If we were unable to parse the query using the schema, we try to gracefully handle it
+				let dataFromModel;
+
+				try {
+					// First we try to parse a JSON with more relaxed rules
+					dataFromModel = jsonParse<IDataObject>(query, { acceptJSObject: true });
+				} catch (error) {
+					// In case of error,
+					// If model supplied a simple string instead of an object AND only one parameter expected, we try to recover the object structure
+					if (Object.keys(schema.shape).length === 1) {
+						const parameterName = Object.keys(schema.shape)[0];
+						dataFromModel = { [parameterName]: query };
+					} else {
+						// Finally throw an error if we were unable to parse the query
+						throw new NodeOperationError(
+							context.getNode(),
+							`Input is not a valid JSON: ${error.message}`,
+						);
+					}
+				}
+
+				// If we were able to parse the query with a fallback, we try to validate it using the schema
+				// Here we will throw an error if the data still does not match the schema
+				parsedQuery = schema.parse(dataFromModel);
+			}
+
+			try {
+				// Call tool function with parsed query
+				const result = await func(parsedQuery);
+
+				return result;
+			} catch (e) {
+				const { index } = context.addInputData(NodeConnectionType.AiTool, [[{ json: { query } }]]);
+				void context.addOutputData(NodeConnectionType.AiTool, index, e);
+
+				return e.toString();
+			}
+		};
+
+		return new DynamicTool({
+			name,
+			description: prepareFallbackToolDescription(description, schema),
+			func: wrappedFunc,
+		});
+	}
+}