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github/json-configuration

v0.1.7MIT

Validate JSON and retrieve configuration values with a local MCP server.

GitHub

JSON configuration

A portable skill and a self-contained local MCP server for checking JSON and looking up values by JSON Pointer.

AssetUse when
json-configuration skillValidating supplied JSON or finding a specific configuration value
validate_json toolChecking syntax and reporting the JSON type or INVALID_JSON
get_json_value toolReading a value by RFC 6901 JSON Pointer, with NOT_FOUND and INVALID_POINTER errors

Install

copilot plugin marketplace add OWNER/REPO
copilot plugin install json-configuration@MARKETPLACE

Replace OWNER/REPO with the GitHub repository that hosts this marketplace and MARKETPLACE with the name in its marketplace.json. See Install plugins for VS Code.

How it works

mcp.json starts node ${PLUGIN_ROOT}/dist/server.mjs over stdio. The committed bundle includes its dependencies, so installed copies don't run npm install. Its third-party licenses are in dist/THIRD_PARTY_NOTICES.txt.

The tool handlers only work on the JSON you pass them: they don't read files, use credentials, make network requests, or save the JSON. That describes this code, not a sandbox. The server is an ordinary Node.js process with your account's permissions, so review any change to its bundle, and remember that Copilot and its model see the JSON you send and the results. Input is limited to 1,048,576 characters, and parse errors don't quote the input. Numbers follow finite JavaScript number rules; overflowing values are rejected instead of becoming null. Represent exact large integers or decimals as JSON strings.

Requirements

Node.js 22.14 or newer on the machine that runs Copilot.

Try it

Use json-configuration to validate {"port":8443} and look up /port.

Develop

Edit src/server.ts, then run npm run build at the repository root to regenerate dist/server.mjs and its notices. npm run verify fails if the committed bundle is stale. Commit the source and generated files together.

Host checks

Before a release, try these by hand in each host you support. Automated tests and evals don't prove that a host loads or shows everything.

  • Ask the skill to validate some JSON and look up a value, and confirm the validate_json and get_json_value tools run.
  • Look up a missing pointer and confirm the answer reports NOT_FOUND instead of guessing.
  • Ask an unrelated question and confirm the tools don't run.