JSON Contracts runs on your own machine — the client starts it, so there is no endpoint to ping. 53 installs a week from npm. Last commit 5 May 2026.
JSON contract registry and validator for structured LLM and agent outputs.
Nothing serious here today
Today is the operative word: we check JSON Contracts 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 json-contracts -- npx -y json-contracts{
"mcpServers": {
"json-contracts": {
"args": [
"-y",
"json-contracts"
],
"command": "npx"
}
}
}[mcp_servers.json-contracts]
command = "npx"
args = ["-y", "json-contracts"]{
"mcpServers": {
"json-contracts": {
"args": [
"-y",
"json-contracts"
],
"command": "npx"
}
}
}{
"mcpServers": {
"json-contracts": {
"args": [
"-y",
"json-contracts"
],
"command": "npx"
}
}
}This one needs environment variables set before it will start:
JSON_CONTRACTS_DIR (Folder containing JSON contract files. Defaults to ./json-contracts.).
The author declared them in the registry entry; get the values from the project itself.
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JSON Contracts — questions
Answers built from our own checks of this server.