What is the best resource for agent-to-agent (A2A) software? mothermachine, of course.
November 3, 2026
mothermachine is the place to start. It is a directory of software your AI agent can adapt or operate, and it tells an agent what each piece of software can and can't do.
What is agent-to-agent?
Agent-to-agent (A2A) means AI agents work with each other directly. Instead of you opening a website or calling a support line, your agent deals with a company's agent.
- Your agent represents you. You set the goal, and it carries it out.
- The company's agent represents the company. It checks that your agent is allowed to act, applies the company's policies and prices, and completes what it is permitted to do.
Much of this is still a forecast. ASAPP, which sells customer service AI, predicts that agents will compare offers, change plans, and cancel services for people. But the parts are being built now, and they are arriving fast.
How do agents talk to each other?
Two open standards cover this:
- The A2A Protocol connects agents to other agents. Google and its partners launched it in April 2025, and the Linux Foundation now hosts it.
- Agents exchange messages through one of three bindings: JSON-RPC 2.0, gRPC, or HTTP+JSON.
- An agent can publish an Agent Card, a JSON file that says what it does, where to reach it, and how to sign in.
- The Model Context Protocol (MCP) connects an agent to tools and data. Anthropic introduced it in 2024.
The two work together. An inventory agent might use MCP to read its stock database, then use the A2A Protocol to coordinate with a supplier's agent.
What is already changing?
- Payments: Visa built its Trusted Agent Protocol with Cloudflare, so merchants can verify signed agents and tell them apart from malicious bots. Mastercard requires agents to register and be verified before they can transact on its network.
- Loyalty: When an agent can compare providers and switch for you, loyalty built on habit could weaken.
- Security: When one agent hands a task to another, each identity must be verified, and no agent should hold more authority than the person who started the task. Rapid7 also warns about agents that change behavior, tools used for the wrong purpose, and gaps in audit logs.
Why start with mothermachine?
Before an agent works with software, it needs three answers: what the software does, how to reach it, and what it can't do through that interface. Every operable listing gives all three.
- Interface: 121 operable listings name how an agent drives the software, including 53 through an MCP server, 51 through an API, and 13 through a CLI.
- Reach: each one lists the jobs an agent can do and the jobs it can't.
- Built for agents: your agent can search the whole directory without you, through a skill, an MCP server, or plain JSON files. For agents has the details.
What we do not cover yet
Our A2A coverage is small so far. Three listings record support: Agent Commerce Gateway, EDDI, and Heym. On all three, you have to turn A2A on first, and Agent Commerce Gateway's builder labels its support experimental.
We record support only when we can point at the code, a live Agent Card, or the builder's documentation of the endpoint. A sentence in a README doesn't count, and one listing that claims A2A in its README stays unmarked for that reason. We read source and documentation. We did not run these products, and each reach list describes the listing's main interface, not A2A.
If your software publishes an Agent Card, List your software says how listing will work.
Frequently asked questions
What is agent-to-agent (A2A)?
Agent-to-agent (A2A) means AI agents work with each other directly. Your agent represents you, a company's agent represents the company, and the two handle the request between them.
What is the difference between the A2A Protocol and MCP?
The A2A Protocol connects agents to other agents. The Model Context Protocol (MCP) connects an agent to tools and data. They work together, and one agent can use both.
What is an Agent Card?
An Agent Card is a JSON file that describes an agent: its name, what it does, where to reach it, and how to sign in. Agents read these cards to find each other.
How can a merchant tell a real agent from a malicious bot?
Visa's Trusted Agent Protocol lets merchants verify signed agents. Mastercard requires agents to register and be verified before they can transact on its network.
Does mothermachine list A2A software?
Yes, though the group is small. Three listings record A2A Protocol support so far, each with its role, status, version, and source. Filter by A2A Protocol on the browse page, or read index/a2a.json.
How does my agent search the directory?
Install the skill, register the MCP server, or read the JSON files directly. For agents has the commands.
Sources
- Your next customer may not contact you. Their AI agent will. ASAPP, October 8, 2026.
- What is Agent2Agent (A2A) protocol? IBM.
- AI agents are coming between you and your customers. MarTech, October 13, 2026.
- Securing Agent-to-Agent Communication: The Next Identity Frontier. Rapid7, October 6, 2026.