Arbiter runs on your own machine — the client starts it, so there is no endpoint to ping. 37 installs a week from npm. Last commit 31 Aug 2026.
Is this transaction safe to sign? Decodes what it really does and answers allow, warn or block.
Nothing serious here today
Today is the operative word: we check Arbiter every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.
Connect this server
This server runs on your own machine — install it with the package manager and the client starts it for you. Package name taken from the official registry entry.
claude mcp add arbiter -e 'ARBITER_PRIVATE_KEY=<ARBITER_PRIVATE_KEY>' -- npx -y @arbiterlabs/mcp{
"mcpServers": {
"arbiter": {
"command": "npx",
"args": [
"-y",
"@arbiterlabs/mcp"
],
"env": {
"ARBITER_PRIVATE_KEY": "<ARBITER_PRIVATE_KEY>"
}
}
}
}[mcp_servers.arbiter]
command = "npx"
args = ["-y", "@arbiterlabs/mcp"]
env = { ARBITER_PRIVATE_KEY = "<ARBITER_PRIVATE_KEY>" }{
"mcpServers": {
"arbiter": {
"command": "npx",
"args": [
"-y",
"@arbiterlabs/mcp"
],
"env": {
"ARBITER_PRIVATE_KEY": "<ARBITER_PRIVATE_KEY>"
}
}
}
}{
"servers": {
"arbiter": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"@arbiterlabs/mcp"
],
"env": {
"ARBITER_PRIVATE_KEY": "<ARBITER_PRIVATE_KEY>"
}
}
}
}Put your own value in place of
<ARBITER_PRIVATE_KEY> (Base64-encoded 64-byte Algorand private key used to pay for calls. The account needs USDC and must be opted in to the USDC asset. Without it every request stops at the paywall).
The author’s registry entry marks it as required.
Optional settings from the registry entry, left out of the block above:
ARBITER_URL (Arbiter deployment to call. Defaults to the hosted service), ARBITER_MAX_SPEND_USD (Lifetime spending cap for this process, in USD. Enforced before anything is signed), ARBITER_MAX_PRICE_PER_CALL (Refuse any single call priced above this, in USD).
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Arbiter — questions
Answers built from our own checks of this server.