agent_sdk

Crate: agent_sdk · Path: crates/agent_sdk
Description (Cargo.toml): Runtime-first SDK for building PromptFleet agents with optional A2A and AG-UI adapters

Role

The public foundation of the PromptFleet agent platform. Provides the agent runtime — skills, tools, services, protocol-neutral message types, and runtime event streams. Protocol adapters (A2A, AG-UI) are enabled through explicit features rather than defining the identity of the crate. The canonical model: build one Agent, compose A2A support with crate::a2a, compose AG-UI support with crate::agui.

Feature flags

From crates/agent_sdk/Cargo.toml:

Feature	Purpose
`default`	`agent-core`
`agent-core`	Runtime-first base; enables `a2a_protocol_core/core`
`a2a-server`	A2A HTTP server transport (Spin on WASM, axum on native)
`a2a-client`	A2A HTTP client transport
`full`	Both `a2a-server` and `a2a-client` with complete testing support
`spec-compliant`	A2A specification compliance mode via `a2a_protocol_core/spec-compliant`
`wasm-optimized`	WASM optimization via `a2a_protocol_core/wasm-optimized`
`file-handling`	File handling support via `a2a_protocol_core/file-handling`
`llm-engine`	LLM tools-first orchestrator with `llm_client` and `llm_tools`
`context-window`	LLM context window management (token budgeting, history strategies); requires `llm-engine`
`a2a-tools`	A2A-native tools (agent/card/get + message/send exposed as LLM tools)
`mcp-client`	MCP tools: connect to external MCP servers. Native: `rmcp` (stdio + streamable HTTP). WASM: `mcp_protocol` (Streamable HTTP via spin-sdk)
`mcp-e2e`	Live E2E tests against real MCP servers (never in default/CI)
`config-loader`	Config loading via `pf_config` (JSON + env)
`agent-observability`	Observability facade wiring; allows `AgentBuilder` to init observability
`redis-storage`	Redis/Valkey task storage for native multi-replica agents
`event-stream`	Native streaming adapters for Agent I/O and A2A SSE
`agui-stream`	Public AG-UI stream surface; built on top of `event-stream`
`sub-agents`	Sub-agent delegation tools (native-only in v1)
`test-support`	Test-only engine seam accessors for cross-crate harnesses
`auto-observability`	Convenience: `config-loader` + `agent-observability`
`interactive-tools`	Typed interaction contracts for reusable ask-question/confirmation flows
`agui-agent`	Capability bundle: `agent-core` + `llm-engine` + `agui-stream`
`a2a-agent`	Capability bundle: `agent-core` + `llm-engine` + `a2a-server` + `a2a-client` + `event-stream`
`dual-agent`	Capability bundle: `agui-agent` + `a2a-agent`
`pf-agent`	Full PromptFleet bundle: `dual-agent` + `mcp-client` + `agent-observability`

Public API (from `src/lib.rs`)

Core re-exports from agent_core:

AgentMessage, ContentPart, ConversationContext, Role, TaskPhase

Agent runtime:

Agent (aliased as AgentRuntime), AgentConfig (aliased as RuntimeConfig)
AgentBuilder — primary entrypoint: AgentBuilder::new("name") or AgentBuilder::from_config_path("agent.json")
AgentHost, AgentHostBuilder — native host composition for serving A2A + AG-UI
SkillEntryBuilder, SkillCall, SkillDefinition, SkillContext
HistoryPolicyConfig, HistoryPolicyMode, HistoryStrategyKind, MessageType

Services and utilities:

ServiceContainer — type-erased dependency injection
CallableSkill — trait for skill handlers
SdkError, SdkResult — error types
TimeoutPolicy — configurable timeout handling
InteractionKind, InteractionOption, InteractionRequest, InteractionResponse

Feature-gated modules:

a2a — A2A-specific types and composition helpers
agui — AG-UI streaming/composition helpers
streaming — native streaming adapters (feature: event-stream)
sub_agent — sub-agent delegation (feature: sub-agents)
mcp_tools — MCP tools integration (feature: mcp-client)
a2a_tools — A2A-native tool helpers (feature: a2a-tools)
observability_runtime — SDK observability flush/runtime helpers (feature: agent-observability)
wasm_kv_task_storage — WASM key-value task storage (feature: a2a-server)
redis_task_storage — Redis/Valkey task storage (feature: redis-storage, native-only)

Macros:

a2a_serve! — zero-boilerplate macro that generates the complete #[http_component] function (WASM only, feature: a2a-server)

Prelude:

agent_sdk::prelude re-exports the most common types

Constant:

SDK_VERSION — crate version from Cargo.toml

Example sketch

use agent_sdk::{AgentBuilder, SdkResult};
use serde_json::json;

fn main() -> SdkResult<()> {
    let mut agent = AgentBuilder::new("weather-agent")?.build()?;

    agent
        .add_skill("get_weather")
        .handler(|params| async move {
            let location = params["location"].as_str().unwrap_or("unknown");
            Ok(json!({"location": location, "temp": 22, "condition": "sunny"}))
        })
        .register()?;

    Ok(())
}

Capability bundles (presets)

These bundle common feature combinations for convenience:

Preset	Includes	Use case
`agui-agent`	`agent-core` + `llm-engine` + `agui-stream`	AG-UI streaming agent
`a2a-agent`	`agent-core` + `llm-engine` + `a2a-server` + `a2a-client` + `event-stream`	A2A-only agent
`dual-agent`	`agui-agent` + `a2a-agent`	Agent serving both A2A and AG-UI
`pf-agent`	`dual-agent` + `mcp-client` + `agent-observability`	Full PromptFleet agent with MCP and observability

LLM Client guide — using llm-engine and context-window
LLM Tools guide — registering tools with #[llm_tool]
A2A Serving guide — setting up A2A server transport
AG-UI Streaming guide — streaming with agui-stream
Sub-Agents guide — delegating to sub-agents
MCP guide — connecting to MCP servers
Configuration guide — using config-loader
Observability guide — wiring agent-observability
Interactive Tools guide — typed interaction contracts
Skills guide — registering and composing skills

Full API reference: cargo doc -p agent_sdk --no-deps --all-features