cadence-sdk 2.0.12

Framework-agnostic SDK for building Cadence AI agent plugins

Write your plugin once — works on LangGraph, OpenAI Agents SDK, and Google ADK.

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What is this?

Cadence SDK lets you build AI agent plugins that are completely decoupled from any orchestration framework. You define tools and domain logic; the Cadence platform handles LLM configuration, routing, and multi-agent orchestration.

A plugin is two things:

• A Plugin (stateless factory) — declares metadata and creates agent instances
• An Agent — holds tools, a system prompt, and optional lifecycle hooks

The SDK provides the base classes, decorators, and types to wire these together.

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Installation

pip install cadence-sdk

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Quick Start

Create my_plugin/plugin.py:

from cadence_sdk import BasePlugin, BaseSpecializedAgent, PluginMetadata, uvtool, plugin_settings, UvTool
from typing import List


class MyAgent(BaseSpecializedAgent):
    def initialize(self, config: dict) -> None:
        self.api_key = config["api_key"]
        self._search_tool = self._make_search_tool()

    def _make_search_tool(self) -> UvTool:
        @uvtool
        def search(query: str) -> str:
            """Search for information."""
            return call_api(query, self.api_key)

        return search

    def get_tools(self) -> List[UvTool]:
        return [self._search_tool]

    def get_system_prompt(self) -> str:
        return "You are a helpful assistant."


@plugin_settings([
    {"key": "api_key", "type": "str", "description": "API key", "sensitive": True, "required": True},
    {"key": "timeout", "type": "int", "description": "Request timeout in seconds", "default": 30},
])
class MyPlugin(BasePlugin):
    @staticmethod
    def get_metadata() -> PluginMetadata:
        return PluginMetadata(
            pid="com.example.my_plugin",
            name="My Plugin",
            version="1.0.0",
            description="Does something useful",
        )

    @staticmethod
    def create_agent() -> MyAgent:
        return MyAgent()

Cadence auto-discovers any BasePlugin subclass in a plugin.py file — no manual registration needed.

Package:

zip -r my_plugin.zip my_plugin/ -x "**/__pycache__/*" "**/*.pyc"

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How to Use

Agents

Every agent must implement two methods:

Method	Purpose
get_tools()	Return a list of UvTool instances
get_system_prompt()	Return the system prompt string

Optional lifecycle hooks:

Method	Purpose
initialize(config)	Set up state when the agent is created; config comes from @plugin_settings
cleanup()	Async teardown — close connections, release resources

Choose which base class to extend:

• BaseSpecializedAgent — tool-focused agent for any multi-agent mode (supervisor, coordinator, handoff)
• BaseScopedAgent — context-anchored agent for grounded mode; requires load_anchor(resource_id) and build_scope_rules(context)
• Both — extend both classes to support grounded and standard modes in one plugin

Plugins

A plugin is a stateless factory. Implement two static methods:

Method	Purpose
get_metadata()	Return a PluginMetadata (pid, name, version, description)
create_agent()	Return a fresh agent instance

Optional static methods: validate_dependencies(), get_settings_schema(), health_check().

Tools

Use @uvtool to wrap any sync or async function as a framework-agnostic tool:

@uvtool
def search(query: str) -> str:
    """Search for information."""
    return do_search(query)


@uvtool(stream=True, validate=True)
async def fetch(url: str) -> dict:
    """Fetch URL content."""
    return await do_fetch(url)

@uvtool accepts: name, description, args_schema (Pydantic model), stream, stream_filter, validate.

Settings

Use @plugin_settings on your plugin class to declare config shown in the Cadence UI:

@plugin_settings([
    {"key": "api_key", "type": "str", "description": "API key", "sensitive": True, "required": True},
    {"key": "max_results", "type": "int", "description": "Max results", "default": 10},
])
class MyPlugin(BasePlugin): ...

Each entry requires: key, type ("str" "int" "float" "bool" "list" "dict"), description.
Optional: name (display label), default, required, sensitive.

Settings are passed to agent.initialize(config) as a dict.

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Best Practices

• Tools as closures — tools that need agent state should be closures inside a _make_* factory method so they capture self
• Stateless plugins — set stateless=True (the default) when agents carry no mutable state; this enables instance sharing across orchestrators
• Declare dependencies — list pip requirements in PluginMetadata.dependencies so the platform auto-installs them on load
• Async cleanup — implement async cleanup() on agents that hold connections or file handles
• Configurable system prompt — add system_prompt to @plugin_settings and return config.get("system_prompt") or default from get_system_prompt()
• Validate in CI — use validate_plugin_structure(MyPlugin) to catch structural issues before deployment

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Examples

Example	Description
web_search_agent	Web search via Serper.dev
recommendation_agent	Product recommendations via Qdrant
helpdesk_agent	Helpdesk support agent
webpage_reader_agent	Web page content reader

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Development

git clone https://github.com/jonaskahn/cadence.git
cd cadence/sdk
poetry install --with dev

# Run tests
PYTHONPATH=src python -m pytest tests/ -v

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MIT Licensed