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Installation

The AP3 SDK is published on PyPI as two packages:

  • ap3 — the protocol surface: types, directives, signing, services, A2A middleware.
  • ap3-functions — the cryptographic operation implementations (currently PSI). Imports as ap3_functions. Pulls in ap3 automatically.

Most users want both. Install ap3-functions and you get ap3 as a transitive dependency.

Prerequisites

  • Python ≥ 3.11, < 3.14

uv is fast and handles virtual environments for you.

uv add ap3-functions

Or, if you only need the protocol surface (no PSI runtime):

uv add ap3

For A2A-based hosting/clients, install the optional extra:

uv add "ap3[a2a]"

If you don't have uv yet:

curl -LsSf https://astral.sh/uv/install.sh | sh

Install with pip

pip install ap3-functions

Or just the protocol surface:

pip install ap3

With the A2A extra:

pip install "ap3[a2a]"

Verify Installation

import ap3
import ap3_functions

print(ap3.__version__)  
print(ap3_functions.__version__)

Dependencies

Pulled in automatically:

  • ap3 — pydantic, httpx, cryptography, protobuf
  • ap3[a2a] extra — a2a-sdk[http-server], grpcio, uvicorn, starlette
  • ap3-functions — depends on ap3; pure-Python PSI implementation built on rbcl (libsodium / Ristretto255) and merlin_transcripts

Working from source

If you want to hack on the SDK itself, clone the repo and use the workspace:

git clone https://github.com/lfdt-ap3/ap3.git
cd ap3
uv sync
source .venv/bin/activate  # macOS / Linux

The SDK source lives under src/ap3/, and ap3-functions lives under packages/ap3-functions/:

ap3/
├── src/ap3/
│   ├── types/          # Core types, directives, and error models
│   ├── core/           # Base Operation contract for protocol implementations
│   ├── signing/        # Ed25519 signing primitives for directives/commitments
│   ├── services/       # Commitment metadata + discovery + compatibility
│   └── a2a/            # A2A middleware (PrivacyAgent, AP3Middleware)
├── packages/
│   └── ap3-functions/  # Protocol implementations (e.g., PSI). Import as `ap3_functions`.
├── examples/           # Working examples
├── tests/              # Test suite
└── docs/               # This documentation

Next Steps

  1. Configure your environment — set up API keys
  2. Quickstart — get started with an end-to-end codelab
  3. API Reference — explore the SDK surface

Support

If you run into issues: