A2A

The A2A (Agent-to-Agent) protocol enables Sim to interact with external AI agents and systems that implement A2A-compatible APIs. With A2A, you can connect Sim’s automations and workflows to remote agents—such as LLM-powered bots, microservices, and other AI-based tools—using a standardized messaging format.

Using the A2A tools in Sim, you can:

Send Messages to External Agents: Communicate directly with remote agents, providing prompts, commands, or data.
Receive and Stream Responses: Get structured responses, artifacts, or real-time updates from the agent as the task progresses.
Continue Conversations or Tasks: Carry on multi-turn conversations or workflows by referencing task and context IDs.
Integrate Third-Party AI and Automation: Leverage external A2A-compatible services as part of your Sim workflows.

These features allow you to build advanced workflows that combine Sim’s native capabilities with the intelligence and automation of external AIs or custom agents. To use A2A integrations, you’ll need the external agent’s endpoint URL and, if required, an API key or credentials.

Parameter	Type	Required	Description
`agentUrl`	string	Yes	The A2A agent endpoint URL
`message`	string	Yes	Message to send to the agent
`taskId`	string	No	Task ID for continuing an existing task
`contextId`	string	No	Context ID for conversation continuity
`data`	string	No	Structured data to include with the message (JSON string)
`files`	array	No	Files to include with the message
`apiKey`	string	No	API key for authentication

Output

Parameter	Type	Description
`content`	string	Text response content from the agent
`taskId`	string	Unique task identifier
`contextId`	string	Groups related tasks/messages
`state`	string	Current lifecycle state (working, completed, failed, canceled, rejected, input_required, auth_required)
`artifacts`	array	Task output artifacts
`history`	array	Conversation history (Message array)

`a2a_get_task`

Query the status of an existing A2A task.

Input

Parameter	Type	Required	Description
`agentUrl`	string	Yes	The A2A agent endpoint URL
`taskId`	string	Yes	Task ID to query
`apiKey`	string	No	API key for authentication
`historyLength`	number	No	Number of history messages to include

Output

Parameter	Type	Description
`taskId`	string	Unique task identifier
`contextId`	string	Groups related tasks/messages
`state`	string	Current lifecycle state (working, completed, failed, canceled, rejected, input_required, auth_required)
`artifacts`	array	Task output artifacts
`history`	array	Conversation history (Message array)

`a2a_cancel_task`

Cancel a running A2A task.

Input

Parameter	Type	Required	Description
`agentUrl`	string	Yes	The A2A agent endpoint URL
`taskId`	string	Yes	Task ID to cancel
`apiKey`	string	No	API key for authentication

Output

Parameter	Type	Description
`cancelled`	boolean	Whether cancellation was successful
`state`	string	Current lifecycle state (working, completed, failed, canceled, rejected, input_required, auth_required)

`a2a_get_agent_card`

Fetch the Agent Card (discovery document) for an A2A agent.

Input

Parameter	Type	Required	Description
`agentUrl`	string	Yes	The A2A agent endpoint URL
`apiKey`	string	No	API key for authentication (if required)

Output

Parameter	Type	Description
`name`	string	Agent display name
`description`	string	Agent purpose/capabilities
`url`	string	Service endpoint URL
`provider`	object	Creator organization details
`capabilities`	object	Feature support matrix
`skills`	array	Available operations
`version`	string	A2A protocol version supported by the agent
`defaultInputModes`	array	Default input content types accepted by the agent
`defaultOutputModes`	array	Default output content types produced by the agent

`a2a_resubscribe`

Reconnect to an ongoing A2A task stream after connection interruption.

Input

Parameter	Type	Required	Description
`agentUrl`	string	Yes	The A2A agent endpoint URL
`taskId`	string	Yes	Task ID to resubscribe to
`apiKey`	string	No	API key for authentication

Output

Parameter	Type	Description
`taskId`	string	Unique task identifier
`contextId`	string	Groups related tasks/messages
`state`	string	Current lifecycle state (working, completed, failed, canceled, rejected, input_required, auth_required)
`isRunning`	boolean	Whether the task is still running
`artifacts`	array	Task output artifacts
`history`	array	Conversation history (Message array)

`a2a_set_push_notification`

Configure a webhook to receive task update notifications.

Input

Parameter	Type	Required	Description
`agentUrl`	string	Yes	The A2A agent endpoint URL
`taskId`	string	Yes	Task ID to configure notifications for
`webhookUrl`	string	Yes	HTTPS webhook URL to receive notifications
`token`	string	No	Token for webhook validation
`apiKey`	string	No	API key for authentication

Output

Parameter	Type	Description
`url`	string	HTTPS webhook URL for notifications
`token`	string	Authentication token for webhook validation
`success`	boolean	Whether the operation was successful

`a2a_get_push_notification`

Get the push notification webhook configuration for a task.

Input

Parameter	Type	Required	Description
`agentUrl`	string	Yes	The A2A agent endpoint URL
`taskId`	string	Yes	Task ID to get notification config for
`apiKey`	string	No	API key for authentication

Output

Parameter	Type	Description
`token`	string	Authentication token for webhook validation
`exists`	boolean	Whether the resource exists

`a2a_delete_push_notification`

Delete the push notification webhook configuration for a task.

Input

Parameter	Type	Required	Description
`agentUrl`	string	Yes	The A2A agent endpoint URL
`taskId`	string	Yes	Task ID to delete notification config for
`pushNotificationConfigId`	string	No	Push notification configuration ID to delete (optional - server can derive from taskId)
`apiKey`	string	No	API key for authentication

Output

Parameter	Type	Description
`success`	boolean	Whether the operation was successful

A2A

Usage Instructions

Tools

`a2a_send_message`

Input

Output

`a2a_get_task`

Input

Output

`a2a_cancel_task`

Input

Output

`a2a_get_agent_card`

Input

Output

`a2a_resubscribe`

Input

Output

`a2a_set_push_notification`

Input

Output

`a2a_get_push_notification`

Input

Output

`a2a_delete_push_notification`

Input

Output

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