io.github.json-contracts/json-contracts

JSON Contracts

Is the JSON Contracts MCP server down? No. It answered initialize and tools/list in the probe of 2026-10-31.

JSON contract registry and validator for structured LLM and agent outputs.

alive probed 2026-11-14 · unchanged since 2026-10-31

8tools

1.3ktokens in Claude Opus 5.5

0.6 %of Claude's 200k window

0.5×the median server

288 msto initialize

7 msto list tools

Run it: npx -y json-contracts@0.1.2 (stdio, probed in a container with the network off)
Host: npmjs.com
Reports itself as: json-contracts 0.1.2
Capabilities: prompts, resources, tools
Instructions: none
Of a 1M window: 0.1 % of a 1M context window
Count: 1.3k tokens in Claude Opus 5.5, exact, measured 2026-10-17. With the Claude Code prefix mcp__…__ on each tool name: 1.4k. The o200k_base estimate is 660. Counted again when the tool definitions change. Method.
Repository: https://github.com/json-contracts/json-contracts
Website: https://github.com/json-contracts/json-contracts#readme
Registry: active, updated 2026-05-05 · registry entry

Most expensive tools

The Claude column scales the o200k estimate of each tool by this server's ratio of exact to estimate, 1.93×.

Tool	≈ Claude tokens	o200k estimate	Share of this server
get_repair_contract	291	151	23 %
get_edit_contract	245	127	19 %
get_json_contract	224	116	18 %
validate_json	168	87	13 %
read_contract	149	77	12 %

Other registry entries on npmjs.com, the ones next to this name; all of them.

Servers that mention contracts.

The result of the latest probe, the tool count and the token cost. The feed has an entry for every probe that changed them.

Stops answering, comes back, tool set or cost changes. One confirmation mail first, a stop link in every mail.