Capabilities Matrix

Note

Most capabilities below are available as standalone crates — you don’t need the full SDK. Feature names match agent_sdk Cargo.toml when the capability is composed through the SDK. WASM / Native indicate supported targets.

Deep dive on A2A JSON-RPC methods: A2A v1.0 compliance.

Agent runtime

Capability	Crate(s)	Feature flag	WASM	Native	Status
AgentBuilder config loading	agent_sdk, pf_config	config-loader	Yes	Yes	Stable
Skills & handlers	agent_sdk, agent_core	agent-core (default)	Yes	Yes	Stable
Message handler	agent_sdk	agent-core	Yes	Yes	Stable
Timeout policy	agent_sdk	agent-core	Yes	Yes	Stable
History policy	agent_sdk, llm_context_core	context-window	Yes	Yes	Stable

LLM

Capability	Crate(s)	Feature flag	WASM	Native	Status
OpenAI-compatible wire format	llm_client	— (always)	Yes	Yes	Stable
Anthropic Messages wire format	llm_client	—	Yes	Yes	Stable
Azure OpenAI auth	llm_client	—	Yes	Yes	Stable
Chat streaming	llm_client	—	Yes	Yes	Stable
Model profiles (families, caps)	llm_client	—	Yes	Yes	Stable
Tool calling (registry + execution)	llm_tools, llm_tool_macros, agent_sdk	llm-engine	Yes	Yes	Stable
Context window management	llm_context_core	context-window (via agent_sdk)	Yes	Yes	Stable

Tip

On native, llm_client uses incremental SSE (reqwest stream). On WASM, streaming responses are buffered then parsed (see llm_client crate docs).

A2A protocol

Summary only — see A2A v1.0 compliance for the method-by-method table.

Capability	Crate(s)	Feature flag	WASM	Native	Status
Core JSON-RPC domain	a2a_protocol_core	core	Yes	Yes	Stable
HTTP server (Spin / Axum)	a2a_http_server, agent_sdk	a2a-server	Yes	Yes	Stable
HTTP client	a2a_http_client, agent_sdk	a2a-client	Yes	Yes	Stable
SSE / streaming (HTTP + protocol)	a2a_http_server, a2a_protocol_core	event-stream / streaming	Partial	Yes	Feature-gated
Task storage (in-memory default; Redis native)	agent_sdk, a2a_protocol_core	redis-storage (optional, native)	Yes	Yes	Stable

Serving

Capability	Crate(s)	Feature flag	WASM	Native	Status
WASM (Spin) A2A server	agent_sdk, a2a_http_server	a2a-server	Yes	—	Stable
Native (Axum) A2A server	agent_sdk, a2a_http_server	a2a-server	—	Yes	Stable
AG-UI streaming surface	agent_sdk	agui-stream (implies event-stream)	—	Yes	Stable
Dual-protocol hosting (A2A + AG-UI)	agent_sdk	dual-agent	—	Yes	Stable

Tools

Capability	Crate(s)	Feature flag	WASM	Native	Status
LLM tool registry	llm_tools	llm-engine	Yes	Yes	Stable
#[llm_tool] macro	llm_tool_macros	llm-engine (with llm_tools)	Yes	Yes	Stable
MCP client	agent_sdk, mcp_protocol	mcp-client	Yes	Yes	Stable
Sub-agent delegation	agent_sdk	sub-agents	—	Yes	Stable
A2A-native tools	agent_sdk	a2a-tools	Yes	Yes	Stable
Web search tool	tool_web_search	—	Yes	Yes	Stable
Interactive tools (typed contracts)	agent_sdk	interactive-tools	Yes	Yes	Stable

Observability

Capability	Crate(s)	Feature flag	WASM	Native	Status
Structured logging	structured_logging, observability, observability_core	agent-observability on agent_sdk	Yes	Yes	Stable
OpenTelemetry	otel, observability	agent-observability enables observability/otel	Yes	Yes	Stable
Prometheus	prometheus (crate), observability	prometheus on observability dependency (not part of default agent-observability)	Yes	Yes	Stable

Configuration

Capability	Crate(s)	Feature flag	WASM	Native	Status
JSON config	pf_config	config-loader on agent_sdk	Yes	Yes	Stable
Environment variables	pf_config	config-loader	Yes	Yes	Stable
Dotenv	pf_config	pf_config/dotenv on the pf_config dependency	Yes	Yes	Stable

Testing

Capability	Crate(s)	Feature flag	WASM	Native	Status
Test harness (native)	pf_test_harness	default empty; enable integrations per feature	—	Yes	Stable
LLM scenarios	pf_test_harness	scenario	—	Yes	Stable
SSE capture / A2A HTTP helpers	pf_test_harness	sse, a2a-http, etc.	—	Yes	Stable

Related docs

• agent_sdk
• a2a_http_server
• llm_client
• pf_test_harness