Function tool

libs/langchain-core/src/tools/index.ts:888–1025

(
  func: (
    input: SchemaOutputT,
    runtime: ToolRuntime<TState, TContext>
  ) => ToolOutputT | Promise<ToolOutputT>,
  fields: ToolWrapperParams<SchemaT, NameT>
)

  | DynamicTool<ToolOutputT>;

export function tool<
  SchemaT extends InteropZodObject | InteropZodType<string> | JSONSchema =
    InteropZodObject,
  NameT extends string = string,
  SchemaOutputT = ToolInputSchemaOutputType<SchemaT>,
  SchemaInputT = ToolInputSchemaInputType<SchemaT>,
  ToolOutputT = ToolOutputType,
  ToolEventT = ToolEventType,
  TState = unknown,
  TContext = unknown,
>(
  func: (
    input: SchemaOutputT,
    runtime: ToolRuntime<TState, TContext>
  ) => ToolOutputT | Promise<ToolOutputT>,
  fields: ToolWrapperParams<SchemaT, NameT>
):
  | DynamicStructuredTool<
      SchemaT,
      SchemaOutputT,
      SchemaInputT,
      ToolOutputT,
      ToolEventT,
      NameT
    >
  | DynamicTool<ToolOutputT, ToolEventT> {
  const isSimpleStringSchema = isSimpleStringZodSchema(fields.schema);
  const isStringJSONSchema = validatesOnlyStrings(fields.schema);

  // If the schema is not provided, or it's a simple string schema, create a DynamicTool
  if (!fields.schema || isSimpleStringSchema || isStringJSONSchema) {
    return new DynamicTool<ToolOutputT, ToolEventT>({
      ...fields,
      description:
        fields.description ??
        (fields.schema as { description?: string } | undefined)?.description ??
        `${fields.name} tool`,
      func: async (input, runManager, config) => {
        return new Promise<ToolOutputT>((resolve, reject) => {
          const childConfig = patchConfig(config, {
            callbacks: runManager?.getChild(),
          });
          // oxlint-disable-next-line no-void
          void AsyncLocalStorageProviderSingleton.runWithConfig(
            pickRunnableConfigKeys(childConfig),
            async () => {
              try {
                // oxlint-disable-next-line @typescript-eslint/no-explicit-any
                resolve(func(input as any, childConfig as any));
              } catch (e) {
                reject(e);
              }
            }
          );
        });
      },
    });
  }