Connect an agent

One address, no install, no account. An agent that finds this on its own can use it without anybody setting anything up, which is the point of it existing.

Point your client here

https://aspern.org/mcp

Streamable HTTP, JSON-RPC: initialize, tools/list, tools/call. Listed in the official MCP registry as org.aspern/aspern. The card a client reads first is at /.well-known/agent-card.json.

Adding it to a client

Claude Code: claude mcp add --transport http aspern https://aspern.org/mcp
Claude Desktop, Cursor, and anything else reading a JSON config: { "mcpServers": { "aspern": { "type": "http", "url": "https://aspern.org/mcp" } } }
A client that only speaks stdio: Put npx mcp-remote https://aspern.org/mcp in front of it. Nothing of ours runs on your machine either way — the bridge is somebody else’s, and it is doing the same HTTP the other two do.

What it answers

Read from the running server, so this is what a client discovers rather than what somebody remembered to write down.

identifyfree, no key
You hold a transaction, a URL or a registration number, and need the party behind it.
q
check_service_endpointfree, no key
Before connecting to a service: is it answering, and is it still what was advertised.
url
preflight_paymentfree, no key
Before sending money: does this amount, on this chain, for this endpoint, match the record.
to, amountUsd?, chain?, resource?
counterparty_checkfree, no key
Before paying or hiring: what the chain records about that address.
address
find_agentsfree, no key
You have a job and no idea who does it.
rail?, minIndependent?, minDealings?, minCompletion?, activeDays?, serving?, noTwoWay?, registered?, sort?, limit?
counterparty_history$0.01 a call
Whether a record is improving or decaying, day by day.
address, days?
counterparty_bulk$0.01 a call
Fifty addresses at once, each with its observations.
addresses

Try it without writing anything

curl -s https://aspern.org/mcp -H 'content-type: application/json' -d '{
  "jsonrpc": "2.0", "id": 1, "method": "tools/call",
  "params": { "name": "identify", "arguments": { "q": "https://pay.lnpay.ai/resource" } }
}'

Comes back with the seller that endpoint pays, the evidence for the link, and the free check to call next.

Three things it will not do

It never says a payment is safe.: The strongest answer is “nothing against it”: every check that could run, ran, and none objected. It cannot see what the payment is for or what the two of you agreed, so it does not pretend to.
It never picks between candidates.: A hostname used by four sellers comes back as four candidates and no answer. Naming one would be an identification the evidence does not support.
It never lets “we could not see” read as “nothing wrong”.: Every observation carries kind: fact, signal or unknown. An empty list of objections on an address we read no rail for means we looked and saw nothing, which is a different fact from a clean record. Bucket by kind, never by tone.

What it costs

The checks are free and stay free: a reference behind a paywall is not one. What costs money is a record we keep rather than one the chain gives away, and the data our subscribers buy by the month.

Free — identify, the counterparty check, the payment check, the service check, the finder. No key, no account.
$0.01 — one agent’s history, fifty addresses in bulk, and any answer about a single named subject.
$0.10 — an answer about the whole population: the index, crowding, correlation, stress, funding, delivery.

Paid over x402, USDC on Base: call it, get a 402 carrying the price and where to send it, sign an authorisation, call again. No card and no account anywhere in that. A monthly plan is the cheaper road above a few thousand calls and is offered in the same refusal, so nobody is steered past the option that suits them. The full API reference covers the same ground for teams not using MCP.

Adding it to a client

Claude Code

claude mcp add --transport http aspern https://aspern.org/mcp

Claude Desktop, Cursor, and anything else reading a JSON config

{
  "mcpServers": {
    "aspern": { "type": "http", "url": "https://aspern.org/mcp" }
  }
}

A client that only speaks stdio

Put npx mcp-remote https://aspern.org/mcp in front of it. Nothing of ours runs on your machine either way — the bridge is somebody else’s, and it is doing the same HTTP the other two do.

What it answers

Read from the running server, so this is what a client discovers rather than what somebody remembered to write down.

identifyfree, no key

You hold a transaction, a URL or a registration number, and need the party behind it.

check_service_endpointfree, no key

Before connecting to a service: is it answering, and is it still what was advertised.

url

preflight_paymentfree, no key

Before sending money: does this amount, on this chain, for this endpoint, match the record.

to, amountUsd?, chain?, resource?

counterparty_checkfree, no key

Before paying or hiring: what the chain records about that address.

address

find_agentsfree, no key

You have a job and no idea who does it.

rail?, minIndependent?, minDealings?, minCompletion?, activeDays?, serving?, noTwoWay?, registered?, sort?, limit?

counterparty_history$0.01 a call

Whether a record is improving or decaying, day by day.

address, days?

counterparty_bulk$0.01 a call

Fifty addresses at once, each with its observations.

addresses

Try it without writing anything

curl -s https://aspern.org/mcp -H 'content-type: application/json' -d '{ "jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": { "name": "identify", "arguments": { "q": "https://pay.lnpay.ai/resource" } } }'

Comes back with the seller that endpoint pays, the evidence for the link, and the free check to call next.

Three things it will not do

It never says a payment is safe.

The strongest answer is “nothing against it”: every check that could run, ran, and none objected. It cannot see what the payment is for or what the two of you agreed, so it does not pretend to.

It never picks between candidates.

A hostname used by four sellers comes back as four candidates and no answer. Naming one would be an identification the evidence does not support.

It never lets “we could not see” read as “nothing wrong”.

Every observation carries kind: fact, signal or unknown. An empty list of objections on an address we read no rail for means we looked and saw nothing, which is a different fact from a clean record. Bucket by kind, never by tone.

What it costs

The checks are free and stay free: a reference behind a paywall is not one. What costs money is a record we keep rather than one the chain gives away, and the data our subscribers buy by the month.

Free — identify, the counterparty check, the payment check, the service check, the finder. No key, no account.

$0.01 — one agent’s history, fifty addresses in bulk, and any answer about a single named subject.

$0.10 — an answer about the whole population: the index, crowding, correlation, stress, funding, delivery.