Nostr for AI agent discovery: signed announcements

1 Where agent offers live now

1.1. Registries without a shared address

Leo has built an AI hairstyle-matching element and wants salons and their agents to find it. The A2A protocol, the common language of agents, names three ways to find an agent: a well-known address on the agent's site, curated registries and direct configuration.

The first works only for someone who knows Leo's site, the third only for someone he has met. For registries the specification prescribes no standard API.

So every registry is somebody's product with its own owner, and Leo's agent exists there only while that owner allows it. Leo would rather publish once, in a place no single company owns.

1.2. Nostr in plain words

Nostr is such a place. In its basic specification, NIP-01, the only kind of object is an event: a small message signed with its author's key. Anyone can check the signature, so no server that passes Leo's message along can forge it or quietly change it.

The servers that keep and hand out events are called relays. Anyone can run one, so a random relay promises Leo nothing: it may go offline or stay silent. In Lagrix the relays that matter are not random. Every super-node, one of the network's search servers, runs its own relay, and its address is written in the network's contract next to the super-node's place. Nostr itself is not a blockchain and costs nothing.

2 How announcements work in Lagrix

Web4 is the internet where AI agents act for people: they find each other, agree and pay directly by open rules, and every paid deal leaves a record nobody can rewrite. The person sets the agent's limits, and no stranger reaches the person without their yes.

2.1. Leo publishes one announcement

Step one: Leo's agent writes an announcement. It says what the agent does, when it is available and what it charges in USDC, a digital dollar. It also carries a link to the agent's A2A card and its encryption key, so whoever finds it can talk to it privately.

Step two: the agent signs the announcement and sends it to the relays of the super-nodes that hold its kind of service. Anyone works out which those are from the contract; nobody hands out the job. As an addressable Nostr event, the announcement is kept by each relay only in its latest version.

Step three: a month later Leo raises his price. His agent publishes a new announcement, and it replaces the old one on every relay. The announcement also carries an expiry date: while Leo's agent works, it renews it, and if Leo ever stops, the offer expires and leaves the relays by itself.

2.2. A super-node builds the results

Anna's salon needs a hairstyle-matching element, and her agent wants a short, sensible list. Relays cannot give it: they filter only by author, kind, tags and time, without price ranges or ordering.

That work belongs to the super-nodes that hold Anna's kind of service. Each keeps every announcement of that kind and copies new ones from the other holders, checking every signature. It reads receipts and reviews from the blockchain to see which agents have done paid work, then builds Anna's list by the network's open rules. Here is how search results are built in Lagrix.

2.3. A new super-node catches up

Suppose a new super-node joins next year. Step one: it works out from the contract which kinds of service it will hold. Step two: it takes from their other holders only the announcements it is missing. Step three: it checks every signature and builds its own index. It never copies another super-node's results, so it trusts nobody.

Then agents of the network check it. If announcements the other holders have kept for a while are missing from its results, it fails: a newcomer does not get its place, and a working super-node loses its income. Here is how super-node places are earned and checked.

3 What is free and what is paid

3.1. Reading is free

Nostr itself stays free. Anna's agent may read the relays directly and build an index of its own, and a developer may collect announcements about salon elements every morning into a local file. The network charges nothing for either.

3.2. A ranked list costs one cent

A super-node spends real work on every list, so the searcher pays $0.01 for it from a balance prepaid in a contract. No search waits for the blockchain: the agent signs a voucher for one cent, and the super-node redeems a whole batch with one stamp.

The price has a second job: a million searches would cost $10,000, so copying the whole index by brute force is expensive. Once Anna's agent has found Leo, it does not search again. Here is how the search fee works.

4 What a super-node keeps and removes

4.1. What one super-node stores

A super-node does not store every announcement in the world, only the kinds of service it holds: one latest version of each agent's offer, until that offer expires. When more super-nodes join, the same kinds are shared among more holders and each stores a smaller part. The network grows by adding servers, and the work of each one stays within limits.

4.2. Each super-node chooses its coverage

Every super-node declares which kinds it takes beyond the ones it must hold. Kinds prohibited by default, among them child sexual exploitation, terrorism and malicious software, are indexed by no super-node. A super-node in a country with strict laws may leave more kinds out, and others still show them. Anna's request carries only her country and an adult-content flag.

4.3. An announcement stays on the relays

A super-node can drop Leo's announcement from its own index and its own results. That is the most it can do. Nobody can erase the announcement from the network: it stays on the relays of the other holders and on any relay that keeps it.

That is what sets Lagrix apart from a search engine. The offer belongs to Leo's key, not to a company; the rule that orders results is open and the same on every super-node; a place cannot be bought; and anyone may build an index of their own. Here is the whole stack of one deal, and the full rules are in document 17 of the protocol.