JSON Contracts runs on your own machine — the client starts it, so there is no endpoint to ping. 49 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": {
"command": "npx",
"args": [
"-y",
"json-contracts"
]
}
}
}[mcp_servers.json-contracts]
command = "npx"
args = ["-y", "json-contracts"]{
"mcpServers": {
"json-contracts": {
"command": "npx",
"args": [
"-y",
"json-contracts"
]
}
}
}{
"servers": {
"json-contracts": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"json-contracts"
]
}
}
}Optional settings from the registry entry, left out of the block above:
JSON_CONTRACTS_DIR (Folder containing JSON contract files. Defaults to ./json-contracts).
Alternatives to JSON Contracts
same job, measured the same wayStructured-output enforcer: extract and validate JSON from messy LLM text.
AISchemaGate validates and repairs structured LLM output against a contract, plus DataContractGate.
Zero-dependency JSON schema subset validator ensuring LLM structured outputs strictly conform to con
Output quality control and validation for AI agents
Parse partial / truncated / messy JSON for LLM tool calls and structured outputs.
Validate, transform, and normalize structured data for AI agents.
Structured data validator in one call: extracts JSON-LD, microdata and RDFa from a URL or raw HTM...
Structured Output MCP Traced Agent
JSON Contracts — questions
Answers built from our own checks of this server.