feat: A2A server support in serve()#179
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Add A2A transport support so the same ADCPHandler can be served over both MCP and A2A protocols with a single flag: serve(MyHandler(), name="my-agent", transport="a2a") Implementation: - ADCPAgentExecutor bridges ADCPHandler to a2a-sdk's AgentExecutor interface, parsing DataPart skill invocations and dispatching to handler methods - create_a2a_server() builds a Starlette app with A2A endpoints (agent card at /.well-known/agent.json, JSON-RPC at /) - TestControllerStore wired into A2A via the same _handle_test_controller dispatch logic MCP uses, so storyboards work over both transports - Transport validation rejects unknown transport strings - Exception details not leaked to callers (security review) 15 tests covering executor dispatch, error handling, test controller integration, agent card generation, and server creation. Closes #175 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- Skip create_a2a_server tests on Python <3.11 (a2a-sdk starlette compat issue: Cannot subclass typing.Any) - Don't leak exception details to A2A callers (security review) - Add transport validation with helpful error message - Restore specific security warning about exposed endpoints - Add handler exception test - Move Task import to top-level (cleanup) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
ADCP requires that if a request contains a context field, the response must echo it back unchanged. Previously handlers had to manually call inject_context() — easy to forget, causing storyboard failures. Now create_tool_caller() automatically injects context after the handler returns, for both MCP and A2A transports. Handlers no longer need to call inject_context() manually (though it's still safe to do so — it won't overwrite if context is already set). Validated: capability_discovery storyboard passes 2/2 over A2A, media_buy_seller passes 7/9 (remaining 2 are test handler issues). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Tested skill-doc DX by having agents build seller/signals/creative agents. Seller doc forced iteration on undocumented schema fields; other docs were shipping-quality. - Seller product example now includes required reporting_capabilities and delivery_measurement fields so agents pass 9/9 first try - Added Common Mistakes entries: reporting_capabilities sub-fields, valid enum values (hourly|daily|monthly), delivery_measurement.provider - Removed inject_context calls from code examples — context passthrough is now automatic in create_tool_caller, so teaching it is wrong - Updated serve() reference to document transport="a2a" and port= kwargs Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
serve(handler, transport="a2a")to serve an ADCPHandler as an A2A agentADCPAgentExecutorbridges ADCPHandler methods to the a2a-sdkAgentExecutorinterface — parses DataPart skill invocations, dispatches to handler methods, returns results as A2A Task eventscreate_a2a_server()builds a Starlette app with agent card + JSON-RPC endpointsTestControllerStoreworks over A2A (same_handle_test_controllerdispatch as MCP), so storyboards will work over both transportsTest plan
Closes #175
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