gskinnerteam/flutter-hatcha-app/a2ui-agent-sdk

Name: a2ui-agent-sdk
Author: gskinnerteam

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Python SDK for building A2UI agents. Use when: working with A2uiSchemaManager, a2ui.a2a.extension, a2ui.a2a.parts, a2ui.schema.constants, SendA2uiToClientToolset, BasicCatalog, CatalogConfig, A2uiStreamParser, InferenceStrategy, A2UI extension negotiation, or protocol constants (A2UI_OPEN_TAG, A2UI_CLOSE_TAG, DEFAULT_WORKFLOW_RULES).

Install

npx vskill@latest install gskinnerteam/flutter-hatcha-app/a2ui-agent-sdk

SKILL.md

a2ui-agent-sdk Package — API Reference

The a2ui-agent-sdk package (v0.2.1) provides Python tools for building A2UI-capable agents. It handles schema management, prompt generation, A2A extension negotiation, DataPart creation, response streaming/parsing, and catalog loading — everything a Python agent needs to emit structured A2UI JSON over the A2A protocol.

When to Use

Building a system prompt with catalog-aware schema injection via A2uiSchemaManager
Activating the A2UI extension during A2A handshake
Creating DataParts from A2UI message dictionaries
Using protocol constants (A2UI_OPEN_TAG, A2UI_CLOSE_TAG, DEFAULT_WORKFLOW_RULES)
Loading catalog schemas from files or bundled resources
Parsing/streaming A2UI responses (v0.8 and v0.9 formats)
Using the experimental SendA2uiToClientToolset with Google ADK

Prerequisite: Read the ai-system skill for the Two-Layer AI Architecture context and how Python agents use this SDK within the hatcha_agent.

Package Structure

a2ui/
├── inference_strategy.py        # Abstract InferenceStrategy base
├── a2a/
│   ├── extension.py             # A2UI A2A extension negotiation
│   └── parts.py                 # DataPart creation/parsing/streaming
├── adk/
│   └── send_a2ui_to_client_toolset.py  # ADK toolset (experimental)
├── basic_catalog/
│   ├── constants.py             # BASIC_CATALOG_NAME, version paths
│   └── provider.py             # BundledCatalogProvider, BasicCatalog
├── parser/
│   ├── streaming.py             # A2uiStreamParser base
│   ├── streaming_v08.py         # v0.8 tag-delimited parser
│   ├── streaming_v09.py         # v0.9 tag-delimited parser
│   ├── payload_fixer.py         # JSON repair utilities
│   └── response_part.py         # ResponsePart model
├── schema/
│   ├── catalog.py               # A2uiCatalog, CatalogConfig, providers
│   ├── catalog_provider.py      # A2uiCatalogProvider interface
│   ├── constants.py             # Tags, versions, workflow rules
│   ├── manager.py               # A2uiSchemaManager
│   ├── validator.py             # Schema validation
│   └── utils.py                 # Bundled resource loading
└── template/
    └── manager.py               # A2uiTemplateManager (not yet implemented)

A2uiSchemaManager

Primary class for generating system prompts with embedded catalog schemas and examples. Implements InferenceStrategy.

Constructor

python

from a2ui.schema.manager import A2uiSchemaManager
manager = A2uiSchemaManager(version="0.9", accepts_inline_catalogs=True)

Parameter	Type	Purpose
`version`	`str`	Protocol version (`"0.8"` or `"0.9"`)
`accepts_inline_catalogs`	`bool`	Whether to accept inline catalog definitions from clients

Methods

Method	Signature	Purpose
`generate_system_prompt`	See below	Build a full system prompt with schema
`get_selected_catalog`	`(client_ui_capabilities?, allowed_components?, allowed_messages?) → A2uiCatalog`	Get catalog filtered by client capabilities
`load_examples`	`(catalog: A2uiCatalog, validate: bool = False) → str`	Load example JSON for prompt injection

`generate_system_prompt`

python

prompt = manager.generate_system_prompt(
    role_description="You are a party planning assistant...",
    workflow_description="Ask the user questions one at a time...",
    ui_description="Use cards and buttons for responses.",
    client_ui_capabilities=None,       # Dict from client metadata
    allowed_components=None,           # List of component names to include
    allowed_messages=None,             # List of message types to include
    include_schema=False,              # Embed full JSON schema
    include_examples=False,            # Embed example payloads
    validate_examples=False,           # Validate examples against schema
)

Usage in This Project

python

# agents/hatcha_agent/base_agent.py
from a2ui.schema.manager import A2uiSchemaManager
_SCHEMA_MANAGER = A2uiSchemaManager(version="0.9", accepts_inline_catalogs=True)
class BaseAgent:
    def __init__(self, ...):
        self.schema_manager = _SCHEMA_MANAGER

Extension Negotiation — `a2ui.a2a.extension`

Handles the A2UI extension handshake within the A2A protocol.

Functions

Function	Signature	Purpose
`try_activate_a2ui_extension`	`(context: RequestContext, agent_card: AgentCard) → Optional[...]`	Match client extension URI against agent card; returns activation or `None`
`get_a2ui_agent_extension`	`() → AgentExtension`	Returns the `AgentExtension` object to include in the agent card

Constants

Constant	Value	Purpose
`A2UI_EXTENSION_BASE_URI`	URI string	Base URI for the A2UI extension
`AGENT_EXTENSION_ACCEPTS_INLINE_CATALOGS_KEY`	`str`	Metadata key for inline catalog support
`AGENT_EXTENSION_SUPPORTED_CATALOG_IDS_KEY`	`str`	Metadata key for supported catalog IDs

Usage in This Project

python

# agents/hatcha_agent/__main__.py
from a2ui.a2a.extension import get_a2ui_agent_extension
agent_card = AgentCard(
    ...
    capabilities=AgentCapabilities(
        extensions=[get_a2ui_agent_extension()],
        streaming=True,
    ),
)
# agents/hatcha_agent/a2ui_protocol.py
from a2ui.a2a.extension import try_activate_a2ui_extension
def activate_a2ui_extension(context, agent_card):
    return try_activate_a2ui_extension(context, agent_card) is not None

DataPart Helpers — `a2ui.a2a.parts`

Converts A2UI message dictionaries to/from A2A DataPart objects.

Functions

Function	Signature	Purpose
`create_a2ui_part`	`(message: dict) → Part`	Wrap a single A2UI message dict as an A2A `DataPart`
`parse_response_to_parts`	`(response: Any) → List[Part]`	Parse a complete response into A2A parts
`stream_response_to_parts`	`(response: AsyncIterable) → AsyncIterable[Part]`	Stream response chunks as A2A parts
`get_a2ui_datapart`	`(parts: List[Part]) → Optional[DataPart]`	Extract the first A2UI DataPart from a list
`is_a2ui_part`	`(part: Part) → bool`	Check if a part is an A2UI DataPart
`has_a2ui_parts`	`(parts: List[Part]) → bool`	Check if any part is A2UI

Constants

Constant	Value	Purpose
`A2UI_MIME_TYPE`	MIME type string	Content type for A2UI DataParts

Usage in This Project

python

# agents/hatcha_agent/a2ui_protocol.py
from a2ui.a2a.parts import create_a2ui_part
def messages_to_parts(messages, catalog_id=None):
    return [create_a2ui_part(_flatten_message(m, catalog_id)) for m in messages]

Protocol Constants — `a2ui.schema.constants`

Tags & Delimiters

Constant	Value	Purpose
`A2UI_OPEN_TAG`	`'<a2ui-json>'`	Opening delimiter for A2UI JSON blocks
`A2UI_CLOSE_TAG`	`'</a2ui-json>'`	Closing delimiter for A2UI JSON blocks
`A2UI_SCHEMA_BLOCK_START`	String	Start marker for schema section in prompts
`A2UI_SCHEMA_BLOCK_END`	String	End marker for schema section in prompts

Workflow Rules

Constant	Value	Purpose
`DEFAULT_WORKFLOW_RULES`	Multi-line string	Standard rules for A2UI response format

Key rules from DEFAULT_WORKFLOW_RULES:

Responses can contain one or more A2UI JSON blocks
Each block wrapped in <a2ui-json> / </a2ui-json> tags
Conversational text allowed between/around blocks
JSON must validate against the provided schema
Top-down component ordering within components lists

Version Constants

Constant	Value	Purpose
`VERSION_0_8`	`"0.8"`	Protocol version 0.8
`VERSION_0_9`	`"0.9"`	Protocol version 0.9 (current)
`SPEC_VERSION_MAP`	`dict`	Maps version → schema file paths

Other Keys

Constant	Purpose
`A2UI_CLIENT_CAPABILITIES_KEY`	Metadata key for client capabilities
`CATALOG_COMPONENTS_KEY`	Key for components in catalog schema
`CATALOG_ID_KEY`	Key for catalog identifier
`CATALOG_SCHEMA_KEY`	Key for catalog schema content
`CATALOG_STYLES_KEY`	Key for catalog styles
`INLINE_CATALOGS_KEY`	Key for inline catalog definitions
`SUPPORTED_CATALOG_IDS_KEY`	Key for supported catalog IDs list
`SURFACE_ID_KEY`	Key for surface identifier

Usage in This Project

python

# agents/hatcha_agent/prompts/shared.py
from a2ui.schema.constants import A2UI_OPEN_TAG, A2UI_CLOSE_TAG, DEFAULT_WORKFLOW_RULES
A2UI_DELIMITER = f"{A2UI_OPEN_TAG}\n{{json}}\n{A2UI_CLOSE_TAG}"

Catalog System — `a2ui.schema.catalog`

A2uiCatalog

Loaded catalog with methods for rendering and pruning.

Method	Signature	Purpose
`render_as_llm_instructions`	`() → str`	Render the catalog as LLM-readable instructions
`with_pruning`	`(allowed_components?, allowed_messages?) → A2uiCatalog`	Return filtered copy
`load_examples`	`(path?, validate?) → str`	Load example JSON from path

CatalogConfig

Configuration for loading a catalog.

python

from a2ui.schema.catalog import CatalogConfig

This is the start of the file. Read the full SKILL.md on GitHub.

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Source

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Popularity

Repository stars: 66
Repository forks: 7
7-day trend score: 21

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Install

SKILL.md

a2ui-agent-sdk Package — API Reference

When to Use

Package Structure

A2uiSchemaManager

Constructor

Methods

generate_system_prompt

Usage in This Project

Extension Negotiation — a2ui.a2a.extension

Functions

Constants

Usage in This Project

DataPart Helpers — a2ui.a2a.parts

Functions

Constants

Usage in This Project

Protocol Constants — a2ui.schema.constants

Tags & Delimiters

Workflow Rules

Version Constants

Other Keys

Usage in This Project

Catalog System — a2ui.schema.catalog

A2uiCatalog

CatalogConfig

Security

Quality evaluation

Source

Popularity

Works with

`generate_system_prompt`

Extension Negotiation — `a2ui.a2a.extension`

DataPart Helpers — `a2ui.a2a.parts`

Protocol Constants — `a2ui.schema.constants`

Catalog System — `a2ui.schema.catalog`