JSON contract registry and validator for structured LLM and agent outputs.
JSON contract registry and validator for structured LLM and agent outputs.
JSON Contracts is a local MCP contract server for natural-language-to-JSON workflows. It gives agents Git-controlled JSON contracts, rules, examples, and JSON Schema validation tools so any model can reliably convert natural-language requests into schema-valid JSON.
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Check the linked publisher documentation and your connected client's tool list. Names and availability can vary with the server version and account permissions.
| Tool | What it does |
|---|---|
| list_contracts | |
| read_contract | Returns the selected contract's description, rules, operations, schema, examples, contractHash, and schemaHash. |
| get_json_contract | The agent/model uses this contract to produce JSON. The MCP server does not produce it. |
| get_edit_contract | The agent/model uses this edit contract to return the complete updated JSON object. The MCP server first validates currentJson against the selected contract, and the agent should validate the edited object with validate_ |
| validate_json | valid is never true unless Ajv validates the JSON against the contract schema. |
| get_repair_contract | The agent/model uses this repair contract to produce corrected JSON. The MCP server does not repair by calling a model. When validation errors are available, instructions also includes deterministic field-specific repair |
| status | Use this to debug host configuration, loaded contracts, and the exact contract/schema hashes in use. |
| reload_contracts |
claude mcp add json-contracts --env JSON_CONTRACTS_DIR=your-value --env API_AUTH_TOKEN=your-value -- npx -y json-contracts| Variable | Description | Required |
|---|---|---|
| JSON_CONTRACTS_DIR | Filesystem location the server is allowed to use. | Optional |
| API_AUTH_TOKEN | Credential the server authenticates with. | Yes |
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