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A2UI Agent implementation

agent_sdks/python/README.md

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A2UI Agent implementation

The agent_sdks/python/src/a2ui directory contains the Python implementation of the A2UI agent SDK.

Core Components (src/a2ui/core)

The src/a2ui/core directory contains the base protocol logic, version management, and schema operations.

Schema Management (src/a2ui/core/schema)

  • manager.py: The A2uiSchemaManager handles loading specification schemas, managing catalogs, and generating system prompts for LLMs.
  • validator.py: Implements A2uiValidator for validating A2UI messages against JSON schemas and protocol rules.
  • catalog.py: Defines A2uiCatalog and CatalogConfig for handling component libraries.
  • payload_fixer.py: Utilities to automatically correct common LLM output issues in A2UI payloads.

Basic Catalog (src/a2ui/basic_catalog)

  • provider.py: Implementation of BasicCatalog for handling the basic A2UI components.

A2A (src/a2ui/a2a)

  • a2a.py: Utilities for creating A2A Parts with A2UI data and managing the A2UI extension URI.

ADK Extensions (src/a2ui/adk)

Support for the Agent Development Kit (ADK) and A2A protocol.

  • send_a2ui_to_client_toolset.py: Implementation of SendA2uiToClientToolset to enable agents to send UI to clients via tool calls.

Running tests

  1. Navigate to the directory:

    bash
    cd agent_sdks/python

  2. Run the tests

    bash
    uv run pytest

Building the SDK

To build the SDK, run the following command from the agent_sdks/python directory:

bash
uv build .

Formatting code

To format the code, run the following command from the agent_sdks/python directory:

bash
uv run pyink .

Disclaimer

Important: The sample code provided is for demonstration purposes and illustrates the mechanics of A2UI and the Agent-to-Agent (A2A) protocol. When building production applications, it is critical to treat any agent operating outside of your direct control as a potentially untrusted entity.

All operational data received from an external agent—including its AgentCard, messages, artifacts, and task statuses—should be handled as untrusted input. For example, a malicious agent could provide crafted data in its fields (e.g., name, skills.description) that, if used without sanitization to construct prompts for a Large Language Model (LLM), could expose your application to prompt injection attacks.

Similarly, any UI definition or data stream received must be treated as untrusted. Malicious agents could attempt to spoof legitimate interfaces to deceive users (phishing), inject malicious scripts via property values (XSS), or generate excessive layout complexity to degrade client performance (DoS). If your application supports optional embedded content (such as iframes or web views), additional care must be taken to prevent exposure to malicious external sites.

Developer Responsibility: Failure to properly validate data and strictly sandbox rendered content can introduce severe vulnerabilities. Developers are responsible for implementing appropriate security measures—such as input sanitization, Content Security Policies (CSP), strict isolation for optional embedded content, and secure credential handling—to protect their systems and users.