JsonMend MCP server
Commit Oct 18, 2026Repair malformed JSON from LLM outputs and validate it against specific JSON Schemas.
Also known as miketusa-ctrl/jsonmend
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- MIT
What is JsonMend MCP?
JsonMend is an MCP server. Repair malformed JSON from LLM outputs and validate it against specific JSON Schemas.
Summary generated from the project's README
About JsonMend MCP server
Fixing broken JSON structures generated by large language models is the primary function of this remote MCP server. Developers can use it to mend malformed syntax and ensure that data outputs strictly adhere to specific JSON Schemas. It operates as a streamable HTTP service, making it accessible to AI clients like Cursor, Windsurf, and Cline without requiring local installation of the core logic.
Users connect to the service via a provided URL using specific configuration settings for their chosen IDE or assistant. For Claude Desktop, you can add it as a custom connector or use the mcp-remote bridge to bridge the connection. The server provides two specific tools: repair_json for fixing syntax errors and validate_json for schema compliance. While it is available as a hosted service, developers can also deploy their own instance using Node.js 22 and Cloudflare Wrangler.
What you can do with it
- 1Fixing broken LLM syntaxSend a malformed JSON string to the server to correct structural errors.
- 2Enforcing data structuresVerify that a generated JSON object matches a predefined schema.
- 3Integrating with AI IDEsConfigure Cursor or Windsurf to use the remote service for automated JSON correction.
Written from the project's README. Every use case is checked against a quote from it.
README
View on GitHubJsonMend
Repair broken JSON from LLM output and validate it against a JSON Schema.
Live service
- Web app and API: https://jsonmend.mike-tusa.workers.dev/
- Plans: Free, no paid plan (https://jsonmend.mike-tusa.workers.dev/)
- Support: digitalpromohub.support@gmail.com
Use it from an AI assistant (MCP)
JsonMend is a remote MCP server (Streamable HTTP) at https://jsonmend.mike-tusa.workers.dev/mcp. Tools: repair_json, validate_json.
Cursor and Windsurf accept this config:
{
"mcpServers": {
"jsonmend": {
"type": "http",
"url": "https://jsonmend.mike-tusa.workers.dev/mcp"
}
}
}
Cline (MCP Servers > Remote Servers, or cline_mcp_settings.json) needs "type": "streamableHttp":
{
"mcpServers": {
"jsonmend": {
"type": "streamableHttp",
"url": "https://jsonmend.mike-tusa.workers.dev/mcp"
}
}
}
Claude Desktop: open Settings > Connectors, choose "Add custom connector" and paste https://jsonmend.mike-tusa.workers.dev/mcp. Or, for clients that only support local (stdio) servers, use the mcp-remote bridge: npx mcp-remote https://jsonmend.mike-tusa.workers.dev/mcp.
VS Code uses a servers key instead of mcpServers.
The server.json file is the MCP Registry manifest for this server.
Run your own copy
Requires Node.js 22+ and a Cloudflare account.
npm install
npx wrangler@4 dev # local dev server
wrangler.toml is a template: create your own KV namespaces / D1 databases / rate-limit namespaces and replace the <PLACEHOLDER> values before npx wrangler@4 deploy. Any secrets the Worker reads go in wrangler secret put (or .dev.vars locally), never in the repo.
License
MIT (c) Digital Promo Hub. See LICENSE.
JsonMend MCP questions
How do I use JsonMend with Cline?
Cline requires the server type to be set to 'streamableHttp' in your configuration.
Can I run my own instance of JsonMend?
Yes, you can run your own copy using Node.js 22+ and a Cloudflare account.
What tools are available in the MCP server?
The server provides two tools: repair_json and validate_json.