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A2A Client Agent

Send tasks to A2A (Agent-to-Agent) servers
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Overview

The A2A Client Agent node enables interaction with Agent-to-Agent (A2A) servers by sending tasks, checking task statuses, or retrieving agent capabilities. It is designed to facilitate communication and orchestration between distributed agents registered in an A2A registry.

Common scenarios where this node is beneficial include:

  • Submitting processing tasks to remote agents for execution.
  • Monitoring the progress or results of previously submitted tasks.
  • Discovering what capabilities a particular agent supports before sending tasks.

Practical examples:

  • Automating workflow steps by delegating specific jobs to specialized agents.
  • Querying an agent to check if it supports certain processing modes or modalities.
  • Polling for completion status of asynchronous tasks sent earlier.

This summary focuses on the Get Agent Capabilities operation, which retrieves detailed information about an agent's supported features.

Properties

Name Meaning
Registry URL URL of the A2A registry used to discover available agents.
Available Agents Select an agent from the discovered list or choose manual configuration.
Agent Server URL URL of the selected A2A agent server; auto-detected if left empty (only shown for manual entry).
Agent Server Port Port number of the A2A agent server (used if Agent Server URL is empty and manual entry chosen).
Advanced Options Collection of optional parameters:
- Client ID Identifier string for this client instance (default "n8n-client").
- Session ID Session identifier for correlating tasks; auto-generated if empty.
- Correlation ID Correlation identifier for tracking tasks; auto-generated if empty.
- Timeout (seconds) Request timeout duration in seconds (default 30).

Output

The node outputs JSON data containing the result of the getCapabilities request to the selected agent. The output fields include:

  • a2a_success: Boolean indicating if the request was successful.
  • a2a_request_id: Unique ID of the JSON-RPC request.
  • a2a_response_id: Response ID matching the request.
  • a2a_agent_id: Identifier of the agent queried.
  • a2a_capabilities: Object listing the agent's capabilities.
  • a2a_supported_protocols: Array of protocols supported by the agent.
  • a2a_supported_modalities: Array of modalities supported by the agent.
  • a2a_processing_modes: Array of processing modes the agent can handle.
  • a2a_response: Full raw response object from the agent.
  • a2a_agent_url: URL of the agent server contacted.
  • a2a_agent_info: Parsed agent metadata from selection.
  • a2a_retrieved_at: Timestamp when capabilities were retrieved.

If the request fails, the output includes error details such as:

  • a2a_success: false
  • a2a_error: Error message string.
  • a2a_error_data: Additional error data if available.
  • a2a_failed_at: Timestamp of failure.

No binary data is produced by this operation.

Dependencies

  • Requires access to an A2A registry service to discover agents (configurable via Registry URL).
  • Requires network connectivity to the selected A2A agent server.
  • Uses HTTP POST requests with JSON-RPC 2.0 protocol to communicate with agents.
  • No explicit credential requirements are defined, but the node sends a client ID header.
  • Timeout and other advanced options can be configured to control request behavior.

Troubleshooting

Common Issues

  • No valid agent selected: Occurs if no agent is chosen or the registry connection failed. Remedy by verifying the registry URL or using manual agent configuration.
  • Invalid agent selection: Happens if the selected agent data cannot be parsed. Ensure the agent option is correctly selected from the dropdown.
  • Timeouts or network errors: May occur if the agent server is unreachable or slow to respond. Adjust timeout settings or verify network connectivity.
  • Invalid JSON-RPC response: If the agent returns malformed or unexpected data, check the agent server health and compatibility.

Error Messages

  • "No valid agent selected. Please check registry connection or use manual configuration."
    Means the node could not find a usable agent endpoint.

  • "Invalid agent selection: <error>"
    Indicates parsing issues with the selected agent info.

  • "Invalid JSON-RPC 2.0 response format"
    The response did not conform to expected JSON-RPC structure.

  • "HTTP <status>: <message>"
    HTTP-level errors from the agent server.

  • "JSON-RPC Error <code>: <message>"
    Errors returned by the agent in JSON-RPC error format.

In all cases, reviewing the agent server logs and network setup helps resolve issues.

Links and References

  • JSON-RPC 2.0 Specification
  • Documentation or API reference for your specific A2A registry and agent implementations (not provided here).
  • n8n community forums and documentation for custom node development and troubleshooting.

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