feat: add experimental A2A server (simple profile) and sample

[Tsuyoshi Ushio (TsuyoshiUshio)]

Summary

Implement the experimental A2A server simple profile from FRD 0009 (#208). Add a runnable sample.

• Opt-in typed config: builtin_endpoints.a2a with mode: simple and an explicit url.
• Per-agent Agent Card (/agents/{name}/.well-known/agent-card.json) and A2A 1.0 JSON-RPC route (/agents/{name}/a2a).
• Only non-streaming SendMessage with user text parts. The response is one direct agent Message.
• Uses the public MAF agent-framework-hosting-a2a conversion and the A2A SDK request handler. Reuses the existing HTTP auth, non-streaming runner, workflow bindings, and runtime sessions.
• Fixed limits for request size, parts, text, response size, and in-flight requests per agent.
• Rejects Tasks, streaming, subscribe/cancel, push notifications, REST, non-text parts, and wire versions other than 1.0.
• docs/design/a2a-server.md describes the design of this PR. Future scope is listed as planned work only.

Sample

samples/a2a-incident-triage has a server and two clients: a MAF A2AAgent client (client.py) and a raw JSON-RPC client (raw_client.py). The client runs in a separate environment, because it needs MAF core 1.15+. The server stays on core 1.13. See the sample README.

Local runs need Azure Functions Core Tools 4.14 or later (see #211).

Dependencies

New [a2a] extra: agent-framework-hosting-a2a==1.0.0a260730, agent-framework-hosting==1.0.0a260730, a2a-sdk[http-server]==1.1.2. Existing pins do not change.

Validation

• ruff, mypy, and generate_config_reference.py --check are clean.
• Unit tests: 1,342 passed.
• Local Functions host test with client.py and raw_client.py passed.

Stack

Base: #208 (FRD only).

[Copilot]

Copilot review overview

🟡 Changes recommended

Critical request-size enforcement and several moderate correctness and validation issues remain unresolved.

Get a fresh assessment by requesting another Copilot review.

Review effort: Lite
Findings: 1 · 1 · 1

Open (3)

• Enforce request size limits before buffering bodies · New
• Install the server A2A extra for E2E tests · New
• Document that mode defaults to simple · New

What changed in this PR

Adds an experimental P3 A2A 1.0 non-streaming server with authenticated routes, typed configuration, isolated client tooling, tests, and documentation.

Changes:

• Adds A2A registration, validation, authentication, limits, and JSON-RPC handling.
• Adds incident-triage samples and real-host interoperability coverage.
• Adds optional dependencies, CI validation, and generated documentation.

Open findings:

• Critical: Request bodies are fully buffered before the advertised size limit is enforced.
• Moderate: E2E setup omits the server A2A extra; malformed ports and trailing-slash URLs are accepted; cached Agent Cards are mutated per request.
• Nit: Front-matter documentation incorrectly requires explicitly specifying mode.

File	Description
tests/​test_registration_endpoints.py	Optional dependency guidance tests
tests/​test_registration_auth.py	A2A authorization scope tests
tests/​test_registration_a2a.py	Protocol, card, route, and limit tests
tests/​test_config_validation.py	A2A URL validation tests
tests/​test_config_schema.py	A2A schema tests
tests/​test_config_merge.py	Configuration merge tests
tests/​test_config_fixtures.py	A2A fixture coverage
tests/​test_app_routes.py	Route and binding tests
tests/​fixtures/​config_scenarios/​20_a2a_simple/​main.agent.md	Simple A2A configuration fixture
tests/​endtoend/​test_a2a.py	Real-host interoperability test
tests/​endtoend/​apps/​a2a-simple/​requirements.txt	E2E server dependencies
tests/​endtoend/​apps/​a2a-simple/​main.agent.md	Deterministic agent configuration
tests/​endtoend/​apps/​a2a-simple/​host.json	E2E host configuration
tests/​endtoend/​apps/​a2a-simple/​function_app.py	Deterministic E2E application
src/​azure_functions_agents/​registration/​endpoints.py	Optional A2A registration
src/​azure_functions_agents/​registration/​a2a.py	A2A cards and JSON-RPC routes; request and card lifecycle findings
src/​azure_functions_agents/​registration/​_auth.py	Scoped authorization support
src/​azure_functions_agents/​config/​validation.py	Trusted URL validation; malformed port finding
src/​azure_functions_agents/​config/​schema.py	Typed A2A configuration
src/​azure_functions_agents/​config/​merge.py	A2A configuration merging
src/​azure_functions_agents/​config/​__init__.py	Public configuration export
src/​azure_functions_agents/​app.py	A2A endpoint discovery and registration
samples/​README.md	Sample catalog update
samples/​a2a-incident-triage/​src/​requirements.txt	Server sample dependencies
samples/​a2a-incident-triage/​src/​main.agent.md	Sample agent configuration
samples/​a2a-incident-triage/​src/​local.settings.template.json	Local settings template
samples/​a2a-incident-triage/​src/​host.json	Sample host configuration
samples/​a2a-incident-triage/​src/​function_app.py	Sample Function App
samples/​a2a-incident-triage/​src/​.funcignore	Sample ignore rules
samples/​a2a-incident-triage/​requirements-client.txt	Isolated client dependencies
samples/​a2a-incident-triage/​README.md	Sample setup and usage
samples/​a2a-incident-triage/​raw_client.py	Raw JSON-RPC client
samples/​a2a-incident-triage/​client.py	MAF A2A client
README.md	User-facing A2A documentation
pyproject.toml	A2A dependency extras
eng/​templates/​jobs/​ci-tests.yml	A2A wheel validation
eng/​scripts/​install_e2e_dependencies.py	E2E dependency setup; missing server-extra finding
eng/​scripts/​generate_config_reference.py	Generated reference support
docs/​index.md	Documentation landing-page update
docs/​getting-started.md	A2A onboarding guidance
docs/​front-matter-spec.md	A2A authoring documentation; mode requirement nit
docs/​front-matter-reference.md	Generated configuration reference
docs/​frds/​README.md	FRD status update
docs/​frds/​0009-a2a-server.md	P3 scope and decisions
docs/​design/​a2a-server.md	A2A architecture
docs/​design/​a2a-implementation-plan.md	Implementation sequencing
docs/​architecture.md	Runtime architecture updates
.gitignore	Isolated E2E environment exclusion

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