[Feat]: Add new CLI for A2A Protocol developer workflow (schema validation, streaming, completions)

[pascal910107]

Is your feature request related to a problem? Please describe.

There is currently no unified CLI workflow for developing and testing A2A Protocol agents. Developers have to rely on ad-hoc scripts or manual API calls to:

• Generate and inspect Agent Cards
• Validate Agent Cards against the protocol specification (e.g., JSON Schema)
• Check connectivity to agent endpoints
• Exercise basic and advanced interactions (single request, interactive sessions, streaming)

This makes the workflow inconsistent, harder to automate in CI, and more error-prone.

Describe the solution you'd like

Introduce a comprehensive A2A CLI tool that streamlines common developer tasks for the A2A Protocol, including:

• Agent Card management:

  • Generate Agent Cards
  • Validate Agent Cards against the protocol specification (JSON Schema validation)
  • View/inspect Agent Cards in a human-friendly format

• Agent interaction & testing:

  • Connectivity checks to agent endpoints
  • Send single messages and display responses
  • Run interactive client-agent sessions
  • Support streaming responses for realistic conversation simulation

• Developer experience:

  • Multiple output formats (JSON, YAML, and plain text)
  • Shell autocompletions
  • Consistent error handling and exit codes for automation/CI usage

Describe alternatives you've considered

• Continuing with separate scripts and manual curl commands for each workflow step.
• Maintaining a small set of narrowly-scoped commands (e.g., only Agent Card validation), but this would not address end-to-end interaction testing.
• Using a generic API client (e.g., Postman) for testing, which does not provide a cohesive CLI experience, schema validation integration, or easy automation.

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[zeroasterisk]

Interesting idea.

We (A2A) do have an inspector and a tck.

• https://github.com/a2aproject/a2a-tck
• https://github.com/a2aproject/a2a-inspector

There are also several other projects which have samples and tooling to get you started with A2A, for example the agent-starter-pack

• https://adventofagents.com/ see a few different posts here
• https://github.com/GoogleCloudPlatform/agent-starter-pack

---

Do you think the inspector and TCK cover the needs you're asking for?