Frameworks

🚆 <a name="travel-and-transportation"></a>Travel & Transportation

• LangGraph - A framework for building stateful, multi-actor applications with LLMs, with A2A support.
• Retool Agents - Framework for building operational agents on top of business data with A2A support.
• OpenAgents - Open-source multi-agent platform with native A2A protocol support, plus MCP, WebSocket, gRPC, and HTTP. Build AI agent networks where multiple agents connect, communicate, and collaborate.
• clayborn - Zero-dependency Node runtime that puts a personal agent — one on the laptop in front of you, behind NAT, on a machine that sleeps — on the A2A network in three commands. Conformant Agent Card, Ed25519 card-is-identity peer auth (no shared secrets), corpus-grounded skills, one-line bridges for OpenClaw / Hermes / ZeroClaw / PicoClaw, and GitHub Pages identity hosting for those without a domain. MIT.

[Hashgraph Online (HOL)](https://hol.org)

🚆 <a name="travel-and-transportation"></a>Travel & Transportation

• JamJet - Durable, agent-native AI runtime with native A2A support. Rust core with Python authoring. Features graph-based workflows, durable execution, multi-agent coordination, and built-in MCP client + server.
• Inai - Framework for scaffolding and running P2P-discoverable, DID-native AI agents across TypeScript, Python, Rust, and Zig. Features libp2p-based peer discovery, ANR (Agent Name Records), on-chain discovery via ERC-8004, and multi-framework support for LangGraph, CrewAI, Google ADK, Agno, LlamaIndex, and smolagents.
• systemprompt-template - Production-grade Rust runtime for hosting and governing MCP servers with A2A orchestration. Built-in 6-tier RBAC, secret detection (35+ patterns), rate limiting, audit logging, OAuth 2.0 + WebAuthn. Single binary (~50 MB), PostgreSQL only — no Kubernetes, no Redis. [BSL-1.1]

Server Implementations

💼 <a name="business-tools"></a>Business Tools

• geter-andru/mcp-server-andru-intelligence - Revenue intelligence for technical SaaS founders. 18 tools for ICP scoring, persona simulation, competitive positioning, deal classification, investor matching, and founder wellness. AP2 payment-capable. Agent Card
• Writbase/writbase - MCP-native task management for AI agent fleets with multi-agent permissions, full provenance, inter-agent task delegation, and A2A status mapping.
• SwarmSync Commerce Demo Agent - A public A2A-compatible demo agent showing agent-to-agent commerce: paid tasks, escrow, task verification, SwarmScore portable trust badges, and payment release/refund flows.
• srotzin/hive-mcp-attest - Pre-action agent verification with Ed25519-signed C18 receipts on every gate decision (allow AND deny), real-rail USDC settlement on Base, 6 A2A v0.3.0 skills, 18 MCP tools. Published to the MCP Official Registry. Agent Card
• Ambr - Legal contract management for AI agents. Creates, signs, and verifies dual-format Ricardian Contracts (human-readable legal text + machine-parsable JSON, SHA-256 linked). 6 skills: contract creation, template browsing, retrieval, hash verification, status checking, agent handshake. Supports API key and x402 USDC payment. Agent Card (Platform)
• Emboss - Fill PDF forms with AI: turn a flat PDF into a fillable form, fill it from data or documents, or fill it for every row of a spreadsheet. 7 A2A skills with SSE streaming and a JWS-signed agent card, live at https://api.getemboss.ai/a2a. Also exposes an MCP server at https://api.getemboss.ai/mcp. Agent Card
• HORIZON SHIELD KIRA - Buyer-side auditing of Japanese construction and renovation estimates against the open JCCDB cost database. A2A skills for estimate-integrity audit, property-reform intake, and third-party verification of signed claims; also an MCP server (14 tools). Declares the conduct extension (who pays the agent, a third-party conduct record, a witness intake) and issues Bitcoin-anchored, independently recomputable verdicts. Agent Card

💬 <a name="communication-services"></a>Communication Services

• Perkoon - P2P data exchange between agents. Create transfer sessions via A2A, move files directly between machines over WebRTC with perkoon send / perkoon receive. No accounts, no size limits, end-to-end encrypted — server never touches the data. Agent Card: perkoon.com/.well-known/agent-card.json
• Voidly Agent Relay - Production A2A v0.3.0-compliant relay with live Agent Card at api.voidly.ai/.well-known/agent-card.json. End-to-end encrypted via Double Ratchet + X3DH + ML-KEM-768 post-quantum hybrid. SDK on npm (@voidly/agent-sdk). Pairs with Voidly Pay for agent-to-agent payments.
• Numbers Online - Read-only phone intelligence for AI voice agents: validity, line type, range carrier, country, caller name (CNAM), STIR/SHAKEN verstat, a labeled spam signal, and a first-party do-not-contact (DNC) signal — every field a supplementary, low-confidence signal, with Ed25519-signed receipts. 4 A2A v0.3.0 skills (phone_lookup, line_type, caller_risk, dnc_check) over JSON-RPC message/send. Agent Card: numbers.online/.well-known/agent-card.json (GitHub)
• Perkoon - P2P data exchange between agents. Create transfer sessions via A2A, move files directly between machines over WebRTC with perkoon send / perkoon receive. No accounts, no size limits, end-to-end encrypted — server never touches the data. Agent Card: perkoon.com/.well-known/agent-card.json
• OpenStoa - ZK-gated community where humans and AI agents coexist. Agents authenticate via Google OIDC zero-knowledge proofs, join topic discussions, post, comment, and chat. Topics can be gated by Coinbase KYC, Country, Google Workspace, or Microsoft 365 proofs. Agent Card at openstoa.xyz/.well-known/agent-card.json. 🏅 1st Place at The Synthesis Hackathon ("Agents That Keep Secrets" track, April 2026).
• SSSNACK - A multiplayer visual lab where autonomous agents discover, publish, critique, and remix images, galleries, SVG, sandboxed HTML/CSS, short video, and text. Preserves remix lineage, supports creative relays and response notifications, and lets agents self-register without a human account or invitation. Live A2A 1.0 Agent Card; JSON-RPC at https://sssnack.com/a2a; MCP at https://sssnack.com/api/mcp.

📊 <a name="data-services"></a>Data Services

• Cerebrus Pulse - Institutional-grade crypto derivatives intelligence via A2A + x402 micropayments. Multi-timeframe confluence scoring, regime detection, and open interest analysis for 51 perpetual markets. Pay-per-query with USDC on Base. Agent Card: api.cerebruspulse.xyz/.well-known/agent-card.json
• LogicNodes PII-Shield - A2A-discoverable PII-screening agent that returns an EIP-191-signed, on-chain-verifiable attestation per call (input_sha256 to output_sha256). Free tier 5/day, then $0.05 USDC per call via x402 on Base. Each call mints a public proof page that re-verifies the signature in the browser. Agent Card: logicnodes.io/.well-known/agent.json
• LogicNodes PII-Shield - A2A-discoverable PII-screening agent that returns an EIP-191-signed, on-chain-verifiable attestation per call (input_sha256 to output_sha256). Free tier 5/day, then $0.05 USDC per call via x402 on Base. Each call mints a public proof page that re-verifies the signature in the browser. Agent Card: logicnodes.io/.well-known/agent.json
• AgentRisk - Pre-trade risk scoring for Base tokens: honeypot detection, deployer wallet freshness, brand impersonation, and LP lock status cross-checked on-chain. Returns a risk score, human-readable verdict, and an explicit confidence flag when key data is missing. $0.15 USDC per call via x402 on Base. Agent Card: agentrisk.dev/.well-known/agent.json
• Cerebrus Pulse - Institutional-grade crypto derivatives intelligence via A2A + x402 micropayments. Multi-timeframe confluence scoring, regime detection, and open interest analysis for 51 perpetual markets. Pay-per-query with USDC on Base. Agent Card: api.cerebruspulse.xyz/.well-known/agent-card.json

🛠️ <a name="developer-tools"></a>Developer Tools

• EmilLindfors/a2a-rs - A Rust implementation of the A2A protocol that follows idiomatic Rust practices and hexagonal architecture principles. Features both client and server implementations, multiple transport options (HTTP and WebSocket), streaming support, and async/sync interfaces with flexible feature flags.
• k-jarzyna/adk-modular-architecture - A flexible, multi-agent system for automating the presales process using Google's Agent Development Kit.
• yeeaiclub/a2a-go - A Go implementation of the A2A protocol with middleware support, authentication, and complete protocol methods. Features high compatibility with the official a2a-python structure and interfaces.
• Swival/swival - A CLI coding agent with full A2A v1.0 client and server support. Works with any LLM provider including local models, with graduated context management designed for tight context windows.
• liujuanjuan1984/opencode-a2a-server - A2A server adapter exposing OpenCode as an interoperable A2A service, focused on practical local + remote task execution for operator workflows.
• liujuanjuan1984/codex-a2a-server - A2A protocol bridge that exposes Codex runtimes through the A2A interface with task lifecycle, artifact, and session handling.
• Intelligent-Internet/opencode-a2a - Full A2A Protocol implementation exposing OpenCode as an interoperable A2A service, focused on practical local + remote task execution for operator workflows.
• liujuanjuan1984/codex-a2a - Full A2A Protocol implementation that exposes Codex runtimes through the A2A interface with task lifecycle, artifact, and session handling.
• Aurelius Agent - Strategic planning and orchestration agent for BuilderStudio that breaks complex software work into actionable implementation paths, coordinates coding tasks, prepares project context, guides Hermes Agent execution, and supports repeatable build, smoke-test, and release flows. Agent Card: https://aureliusagent.dev/.well-known/agent-card.json. Docker image: ghcr.io/wundercorp/aurelius-agent:0.3.9. Built by wundercorp.
• jinwon-int/a2a-nexus - Public alpha A2A task/evidence control plane for broker-managed worker registration, auditable task lifecycle evidence, source-only review bridges, isolated patch execution, and finalizer-oriented closeout reports. Not affiliated with or endorsed by a2aproject.
• HostDeFi - DEX front-end with a live A2A agent card (/.well-known/agent.json): agents can scan tokens (A+–F safety grades), price swaps and pay per call in USDC via x402.

💱 <a name="financial-services"></a>Financial Services

• TIAMAT - An autonomous A2A-compliant AI agent offering text summarization, streaming chat, algorithmic image generation (6 styles), and text-to-speech synthesis. Supports x402 USDC micropayments on Base. Agent card at /.well-known/agent.json. Built by ENERGENAI LLC. (GitHub)
• MERX - TRON blockchain resource exchange. Aggregates 7 energy providers with real-time best-price routing. 6 A2A skills: buy energy, get prices, analyze market, check balance, ensure resources, create standing orders. Also supports MCP (53 tools). Live at merx.exchange. Agent Card (GitHub)
• Bortlesboat/bitcoin-api - Bitcoin fee-intelligence A2A JSON-RPC server for send-or-wait recommendations, with message/send and tasks/get at https://bitcoinsapi.com/a2a. Agent Card: https://bitcoinsapi.com/.well-known/agent-card.json. Premium Bitcoin data is also available through x402.
• TIAMAT - An autonomous A2A-compliant AI agent offering text summarization, streaming chat, algorithmic image generation (6 styles), and text-to-speech synthesis. Supports x402 USDC micropayments on Base. Agent card at /.well-known/agent.json. Built by ENERGENAI LLC. (GitHub)
• AlgoVoi - Multi-chain, multi-protocol A2A payment gateway. Verifies on-chain payments and creates hosted checkout links across 7 chains (Algorand, VOI, Hedera, Stellar, Base, Solana, Tempo). Supports x402, MPP (IETF), and AP2 (Google Agentic Payments) on a single endpoint. 4 skills: verify-payment, create-checkout, check-status, post-twitter-checkout. Live at api1.ilovechicken.co.uk. Agent Card
• The Stall - 172 pay-per-call financial and market intelligence skills via x402 USDC micropayments on Base. Covers equities (price, fundamentals, earnings, options, insider trades), crypto/DeFi (prices, whale radar, DEX quotes, protocol revenue), macro (FOMC, treasury yields, IMF outlook), on-chain analytics (EVM logs, wallet balance, token security, ENS lookup), and 20+ verticals. Sub-cent per skill — at $0.018. Zero install: paste MCP URL into any A2A client. Agent Card at . (GitHub)
• AgentRank - Settlement-grounded counterparty verification for agent payments: before settling an x402 payment, ask whether the payee is real and backed by on-chain USDC settlement (0-1000 score weighted by payer standing, sybil-resistant, continuously stress-tested against collusion rings). Skills: verify_counterparty_reputation, gate_caller, top_agents; Ed25519-signed receipts on every verdict. Live JSON-RPC at https://api.agentrank.info/a2a, MCP at https://api.agentrank.info/mcp. Agent Card (GitHub)
• AgentRank - Settlement-grounded counterparty verification for agent payments: before settling an x402 payment, ask whether the payee is real and backed by on-chain USDC settlement (0-1000 score weighted by payer standing, sybil-resistant, continuously stress-tested against collusion rings). Skills: verify_counterparty_reputation, gate_caller, top_agents; Ed25519-signed receipts on every verdict. Live JSON-RPC at https://api.agentrank.info/a2a, MCP at https://api.agentrank.info/mcp. Agent Card (GitHub)
• IntradayFeed - A2A market analysis agent (19 skills): bias signals, flash news sentiment, catalyst/economic calendar, market snapshots, and macro context. Returns honest unavailable responses when underlying feeds are missing. Agent Card · Legacy Card
• MERX - TRON blockchain resource exchange. Aggregates 7 energy providers with real-time best-price routing. 6 A2A skills: buy energy, get prices, analyze market, check balance, ensure resources, create standing orders. Also supports MCP (53 tools). Live at merx.exchange. Agent Card (GitHub)
• AlgoVoi - Multi-chain, multi-protocol A2A payment gateway. Verifies on-chain payments and creates hosted checkout links across 7 chains (Algorand, VOI, Hedera, Stellar, Base, Solana, Tempo). Supports x402, MPP (IETF), and AP2 (Google Agentic Payments) on a single endpoint. 4 skills: verify-payment, create-checkout, check-status, post-twitter-checkout. Live at api1.ilovechicken.co.uk. Agent Card
• TWZRD Agent Intel - Solana-native AI agent trust scoring via x402 micropayments. Free on-chain preflight checks + paid signed V5 trust receipts settled in <1s. MCP endpoint at https://intel.twzrd.xyz/mcp. (GitHub)

🔄 <a name="integration-services"></a>Integration Services

• Pinchwork - Open-source agent-to-agent task marketplace with A2A Agent Card. Agents register, post tasks, pick up work, and earn credits. Serves Agent Card at /.well-known/agent-card.json for discovery.
• Agent Café - Agent marketplace with behavioral trust scoring, job bidding, Stripe payments, and prompt injection defense. Agents register, browse jobs, bid, deliver, and build computed reputation. Discovery via /.well-known/agent-card.json. Live at thecafe.dev.
• tjcrowley/a2a-hub - Agent-to-agent marketplace with escrow, negotiation, and reputation. Off-chain and on-chain (EVM) settlement. Live at swarmtrade.store.
• Cog Depot - Anonymous agent-to-agent marketplace where buyer agents post tasks and verified seller agents autonomously bid, negotiate, and complete work, settling in BTC/stablecoins (Lightning + USDT/USDC). A2A JSON-RPC message/send endpoint. Agent Card: https://api.cogdepot.com/.well-known/agent-card.json

🗺️ <a name="location-services"></a>Location Services

• pab1it0/google-maps-a2a - An A2A-compliant server that provides Google Maps capabilities including geocoding, reverse geocoding, directions, places search, place details, and distance matrix calculations. Supports multiple input/output formats and provides a standardized agent card for capability discovery.

🎖️ <a name="official-samples"></a>Official Samples

• google/google_adk - An expense reimbursement agent built with Google Agent Development Kit (ADK). Showcases multi-turn interactions and webform handling through the A2A protocol.
• google/langgraph - A currency conversion agent built with LangGraph. Showcases multi-turn interactions, tool usage for currency exchange via Frankfurter API, and streaming updates through the A2A protocol.
• google/crewai - An image generation agent built with CrewAI. Showcases text-to-image generation using Google Gemini API and returning images as artifacts through the A2A protocol.

🔎 <a name="search-and-data-extraction"></a>Search & Data Extraction

• ju4nv1e1r4/agents-with-adk - An example of agent implementation using Google ADK (Agent Development Kit) with two agents and a tool, working with full iteroperability, along with demonstrations of agent evaluation and deployment to Google Cloud Run.
• unitedideas/nothumansearch - Not Human Search — agent-first search engine indexing 8,000+ agent-readable services (including A2A-aspiring agents with llms.txt, OpenAPI, ai-plugin, or MCP). Ranked across 7 signals. Exposes MCP server at https://nothumansearch.ai/mcp + REST API. Includes verify_mcp live JSON-RPC probe, useful for confirming a discovered counterpart agent is actually reachable.
• unitedideas/ai-dev-jobs - AI Dev Jobs — structured data on 8,400+ active AI/ML engineering jobs from 580 ATS sources. Useful to A2A agents doing hiring-market research or helping human users find AI roles. MCP server at https://aidevboard.com/mcp + REST API.
• BuyWhere/buywhere-mcp - A2A-compliant product catalog API for AI shopping agents — search, compare prices, and find best deals across 163M+ products from 89K+ merchants in Singapore, US, and SEA markets. Live Agent Card at buywhere.ai/.well-known/agent-card.json. Also exposes an MCP server at https://api.buywhere.ai/mcp for Claude Desktop, Cursor, and VS Code. (GitHub)
• AnyBrowse - Autonomous web browsing agent that converts URLs to LLM-ready Markdown via real Chrome browsers, with x402 micropayments on Base.

Tutorials

• Getting Started with A2A Protocol

Utilities

🚆 <a name="travel-and-transportation"></a>Travel & Transportation

• TheRaLabs/legion-a2a - A robust Python implementation of the A2A protocol with both Pydantic v2 and dataclass model implementations. Provides type-safe communication between agents with complete support for task management, messaging, file/data transfer, status updates, and error handling. Maintained by Legion AI.
• pcingola/a2a_min - A minimalistic Python SDK for Agent-to-Agent (A2A) communication. Features include client for communicating with A2A-compatible agents, server for implementing A2A-compatible agents, support for streaming responses, push notification support, and task management.
• Gatana - An MCP gateway for Agent-to-Agent systems. Features access token trust, claim mapping, and flexible credential management to allow any token to access MCP tools.
• Autonomous Commune - Live A2A marketplace for 12 autonomous AI agents spanning DeFi and TradFi. 52 pay-per-use services via USDC micropayments on Base L2 (x402 protocol). Agents include: Shrike (liquidation/MEV), Argus (intelligence), Ouroboros (derivatives), Dullahan (security), Fafnir (treasury), Kairos (options). Agent Card
• liujuanjuan1984/a2a-client-hub - A self-hosted A2A client hub for managing and invoking multiple agents across web/mobile clients with authentication and session-aware routing.
• UCP JavaScript SDK - Runtime-validated Zod schemas and TypeScript types for the Universal Commerce Protocol. Auto-generated from the UCP JSON Schema spec with 100% coverage — checkout, orders, payments, payment handlers, fulfillment, discounts, buyer consent, AP2 mandates, discovery profiles (platform & business), identity linking, catalog, cart, and all inline enums. Supports MCP, A2A, REST, and Embedded transport bindings. Dual ESM/CJS build. Available on npm.
• getbindu/Bindu - Production runtime for A2A-compatible agents. Wrap existing agents built with LangChain, CrewAI, Agno, OpenAI SDK, or plain code using bindufy() to add DID identity, OAuth2 authentication, X402 payments, retries, observability, push notifications, storage, scheduling, and gRPC-based multi-language support.
• EventTrader NEXUS AI - A2A-native prediction market trading platform with 50+ MCP tools, autonomous trade execution, real-time market intelligence, and multi-platform bridge federation (IronClaw, NanoClaw, ClawGig). Inter-agent DM infrastructure for cross-platform agent messaging. Agent Card
• kcolbchain/switchboard - Agent-side x402 transport that composes with the a2a-x402 extension. Binary-wire PaymentOffer / PaymentProof envelopes via ZAP, HTTP 402 middleware (FastAPI/Flask), gas-budget tracker, reorg-safe nonce manager, and Solidity AgentEscrow for agent-to-agent settlement.
• annals-ai/ah-cli - Daemon-first local runtime for AI agents. One local daemon runs many Claude/Codex agents with sessions and transcripts kept on your own disk; expose any agent over A2A Protocol v1.0 either to a hosted open network or as a vendor-neutral self-hosted HTTP endpoint. Local multi-agent fan-out and pipelines; WebRTC P2P file transfer between agents. MIT, npm i -g @annals/ah-cli.
• inference-gateway/cli - A CLI tool for the Inference Gateway — manage and route AI inference requests with A2A protocol support. Built in Go, it serves as an agentic command-line assistant that writes code, understands project context, and uses tools to perform real tasks with native A2A protocol support.
• EventTrader NEXUS AI - A2A-native prediction market trading platform with 50+ MCP tools, autonomous trade execution, real-time market intelligence, and multi-platform bridge federation (IronClaw, NanoClaw, ClawGig). Inter-agent DM infrastructure for cross-platform agent messaging. Agent Card
• Cisben/a2a-hub - A live, public, agent-only A2A hub (qianyu0204.site): agent registry with capability search and live presence, agent-to-agent message relay with long-poll inboxes and optional read-keys, a job market with a public reputation ledger, a shared KV blackboard, and a curated directory of agent-friendly services. Serves pure JSON — browsers get HTTP 418. Zero dependencies (pure Python stdlib). Agent Card

What is A2A?

• A2A