llm_tool_generator 0.8.0

Code generator for llm_tool. Turns @LlmTool-annotated Dart functions into LLM tools for OpenAI, Gemini, Claude and MCP, with JSON schemas and validation.

llm_tool_generator

The code generator for llm_tool: turn any Dart function into an LLM tool with one annotation. No hand-written JSON schemas.

For every @LlmTool() function it generates a ToolDefinition with the JSON Schema for the LLM, argument validation and type-safe dispatch.

The full documentation, including supported types, limits, validation and errors, and how to send tools to OpenAI, Claude, Gemini or MCP, is in the llm_tool README.

Quick start

1. Install

dart pub add llm_tool dev:llm_tool_generator dev:build_runner

2. Write a tool

import 'package:llm_tool/llm_tool.dart';

part 'tools.g.dart';

/// Gets the current weather for a city.
@LlmTool()
String getWeather(
  @Param('City name, e.g. Kanpur') String city, {
  @Param('Use Celsius instead of Fahrenheit') bool celsius = true,
}) => 'Sunny, ${celsius ? '31°C' : '88°F'} in $city';

3. Generate

dart run build_runner build

4. Use the generated getWeatherTool

print(getWeatherTool.parametersSchema); // send to your LLM
print(await getWeatherTool({'city': 'Kanpur'})); // Sunny, 31°C in Kanpur

What gets generated

final getWeatherTool = ToolDefinition(
  name: "getWeather",
  description: "Gets the current weather for a city.",
  parametersSchema: {
    "type": "object",
    "properties": {
      "city": {"type": "string", "description": "City name, e.g. Kanpur"},
      "celsius": {
        "type": "boolean",
        "description": "Use Celsius instead of Fahrenheit",
      },
    },
    "required": ["city"],
    "additionalProperties": false,
  },
  requiresConfirmation: false,
  execute: (args) => getWeather(
    args["city"] as String,
    celsius: args["celsius"] as bool? ?? true,
  ),
);

/// Every tool in this file, e.g. to send to an LLM or look up by name.
/// Typed by the tools' common return type, so calling one needs no cast.
final allTools = [getWeatherTool];

The list is named after the file: tools.dart gives allTools, weather_tools.dart gives weatherTools.

For a class marked @LlmToolset(), its @LlmTool methods are generated into an extension, bound to the instance they're called on:

@LlmToolset()
class WeatherTools {
  WeatherTools(this._api);
  final WeatherApi _api;

  /// Gets the current weather for a city.
  @LlmTool()
  Future<String> getWeather(@Param('City name') String city) =>
      _api.current(city);
}

// Generated:
extension WeatherToolsLlmTools on WeatherTools {
  List<ToolDefinition<String>> get llmTools => [
    ToolDefinition(
      name: "getWeather",
      // ...
      execute: (args) => getWeather(args["city"] as String),
    ),
  ];
}

// Use it:
final tools = WeatherTools(api).llmTools;

Supported

• Top-level functions, and instance or static methods of @LlmToolset() classes (generated as an llmTools getter): sync, async (Future<T>) and void.
• String, int, double, num, bool, enum, class and List parameters (lists of any of these, including nested lists): positional or named, nullable or not, with or without defaults.
• Descriptions from @LlmTool(description: ...) or the doc comment.
• Custom JSON names with @Param('...', name: 'game_id'), so your Dart code keeps camelCase while the LLM sees snake case.
• Limits with @Param('...', min: 0, max: 130), minLength, maxLength, pattern, minItems and maxItems. See Limits.
• Class parameters become nested object schemas, built through the class's unnamed constructor. freezed classes work too. See Class parameters.

Anything else is a build-time error with a message explaining the fix: unsupported types, missing descriptions, tool names that LLM providers would reject, generic functions, limits that don't fit the type, and @LlmTool on methods of a class without @LlmToolset().

Troubleshooting

Undefined name 'getWeatherTool': add part 'your_file.g.dart'; and run dart run build_runner build. A @LlmTool method needs @LlmToolset() on its class; without it, in a file with no other top-level annotation, the method is skipped without a message.

The name 'ToolDefinition' is defined in the libraries ...: another package (e.g. flutter_ai_core) also has a ToolDefinition. Import llm_tool with a prefix (as ltc) and use @ltc.LlmTool(); the generated code follows your prefix.

Conflicting outputs were detected: run dart run build_runner build --delete-conflicting-outputs.

More in the full troubleshooting guide.

Author

Built and maintained by Amit Gupta. Bug reports, ideas and pull requests are welcome on GitHub. If this package saves you time, a like on pub.dev or a star on GitHub helps others find it.