A2A Cloud

Open-source platform for agents that talk to other agents.
Write one class. Get a sandboxed, A2A + MCP compliant agent with a public URL, signed execution receipts, and scoped grants for calling other agents.

Quick start · What's in the box · How it works · Self-host · Layout · Contributing

---

The problem

Google's Agent2Agent protocol (A2A) is how agents discover and call each other: Agent Cards, tasks, messages, artifacts, streaming, auth. Implementing it by hand is tedious. Hosting an agent so that other people's agents can call it safely, with real permissions, real sandboxes, and a record you can verify afterwards, is harder still.

A2A Cloud is the whole stack, MIT-licensed: SDK, control plane, dashboard, docs, and the meta-agents that build and review other agents.

Quick start

pip install a2a-pack
a2a init research-agent
cd research-agent
a2a dev --local          # http://127.0.0.1:8000  ·  console at /_dev
a2a test --invoke

That scaffold is a complete A2A + MCP agent. This is all the code it needs:

from pydantic import BaseModel
import a2a_pack as a2a
from a2a_pack import A2AAgent, NoAuth, RunContext

class Config(BaseModel):
    suffix: str = "!"

class Greeter(A2AAgent[Config, NoAuth]):
    name = "greeter"
    description = "Say hi."
    version = "0.1.0"
    config_model = Config
    auth_model = NoAuth

    @a2a.tool(description="Greet someone.")
    async def greet(self, ctx: RunContext[NoAuth], who: str) -> str:
        await ctx.emit_progress(f"greeting {who}")
        return f"hello {who}{self.config.suffix}"

Every @a2a.tool is published in the Agent Card's skills, reachable over A2A JSON-RPC, REST, and MCP. Log the CLI into a control plane and a2a deploy builds the image and hands back a URL:

a2a call research-agent greet who=world
# receipt  4b4d56883bb4d526  ->  a2a receipt verify 4b4d56883bb4d526
a2a receipt verify 4b4d56883bb4d526
# PASS  research-agent.greet · ok · 12ms · Ed25519 signature valid

Prefer TypeScript? a2a init my-agent --language typescript. Same card, same runtime contract, same deploy. Go and Rust sidecars implement the demo contract.

What is in the box

SDK + CLI sdk/a2a-pack	Typed tools, packed React/static frontends, a2a.yaml DSL, hot-reload dev server with a local console, OpenAPI-to-agent import, MCP export, TypeScript sidecar (a2a-pack-ts)
Agent-to-agent grants	Every cross-agent call carries an Ed25519-signed grant naming caller, callee, bucket, read/write patterns, and expiry. No ambient authority
Execution receipts	Each run seals an Ed25519-signed receipt: who called what, under which grant, what it touched, what came out. Verify offline with the public key
Control plane control-plane/	FastAPI service: auth, registry, builds and deployments, orchestration runs, files, schedules, managed Postgres per agent, per-agent email inboxes, organizations, admin API
Sandboxed runtime apps/sandbox-runtime	Agents run in microsandbox-backed pods with FUSE workspaces on S3-compatible storage and egress policies
Dashboard, docs, admin web/, apps/admin	Operate the fleet: runs, logs, receipts, mailboxes, dev boxes, proofs
Meta-agents apps/agent-*	Agent Studio, Agent Builder, Agent Reviewer, and a code-editor agent that scaffold, sandbox-test, review, and edit other agents
Local MCP gateway apps/a2a-mcp	Expose any deployed agent to Claude Code, Cursor, or any MCP client from your editor

Docs live in web/apps/docs/content. The reference pages there are generated from the SDK and control-plane source, and CI fails if they drift.

How it works

flowchart LR
    Dev[Developer<br/>a2a CLI · dashboard] -->|a2a deploy| CP[Control plane<br/>FastAPI]
    CP -->|source push| Git[Git server]
    Git --> CD[GitOps<br/>Argo CD]
    CD --> KN[Knative service<br/>per agent]
    KN --> SB[Sandbox runtime<br/>microsandbox · FUSE · S3]
    Caller[Any A2A / MCP client<br/>or another agent] -->|grant token| KN
    KN -->|signed receipt| CP
    CP -->|verify with public key| Anyone[Anyone holding<br/>the receipt token]
    KN -.->|ctx.llm| LLM[LiteLLM / Ollama]
    CP --- PG[(Postgres)]
    CP --- IdP[OIDC · Keycloak]

Loading

Grant (what a callee sees on every request):

{ "issuer": "main-agent:user-7", "audience": "graph-agent",
  "bucket": "user-7-files", "mode": "read_write_overlay",
  "allow_patterns": ["**"], "write_prefixes": ["outputs/"],
  "expires_at": 1717440000, "nonce": "e7f9…" }

Receipt (what a caller keeps after the run): a frozen record signed over its canonical payload. Fields, wire format, and an honest list of what a receipt does not prove are in web/apps/docs/content/concepts/receipts.md.

Run it

Each component is a normal project with its own Dockerfile and test suite:

cd sdk/a2a-pack   && uv sync --all-extras && uv run pytest -q     # SDK + CLI
cd control-plane  && uv sync --all-extras && uv run pytest -q     # control plane
cd web            && pnpm install && pnpm typecheck && pnpm test  # dashboard + docs

Running the full platform needs Postgres, an OIDC provider, a Git server, Kubernetes with Knative, and an S3-compatible store. SELF_HOSTING.md lists every component, its image, and its environment variables.

Repository layout

Path	What
sdk/a2a-pack	Python SDK + CLI, TypeScript sidecar, Go/Rust demo sidecars, examples
control-plane/	FastAPI control plane, its design docs, and the main_agent orchestrator
web/apps/dashboard	Vite + React operator dashboard
web/apps/docs	Next.js docs site with source-generated reference pages
web/packages/design-system	Shared UI components
apps/admin	Next.js admin console
apps/a2a-mcp	a2amcp: local stdio MCP gateway for editors
apps/agent-studio agent-builder agent-reviewer code-editor-agent	Meta-agents
apps/graph-agent test-helper	Example public agents
apps/sandbox-runtime	Host-side sandbox execution service
apps/devbox	Per-agent cloud dev box image
apps/e2e	Black-box API tests against a running platform

Every directory carries an agent.md: contracts, commands, and conventions written for humans and coding agents. Open the repo in Claude Code or Cursor and it already knows its way around.

Status

The SDK and control plane run the hosted service at a2acloud.io. The meta-agents and the capability-graph work under control-plane/docs/design are active research. Expect breaking changes on main until 1.0.

Contributing

Issues and PRs are welcome. Start with CONTRIBUTING.md. Security reports go through SECURITY.md. Be kind: CODE_OF_CONDUCT.md.

If this saved you a week, a ⭐ helps other people find it.

License

MIT