Developers

Call the verdict from anywhere

ArbiterQA is headless and agent-native. Drive it from the arbiterqa npm CLI, an MCP client, or the public catalog API — name checks and sets by the same ids you see in the catalog and get a structured pass, fail, or error back.

npm CLI

npx arbiterqa

The CLI wraps the same API. Install nothing to try it, authenticate once, then run checks or sets in CI. Published on npm.

install

# Run without installing
npx arbiterqa --help

# Or add it to your project
npm install --save-dev arbiterqa

authenticate

# Authenticate the CLI (opens the browser, lands on /cli-success)
npx arbiterqa login

run in CI

# Run a single check against a URL
npx arbiterqa run \
  --url https://example.com \
  --validation font-size-body-min-max

# Run a whole validation set and fail CI on a failed verdict
npx arbiterqa run \
  --url https://example.com \
  --set accessibility-compliance \
  --fail-on fail

MCP

Model Context Protocol

Point any MCP client at the hosted endpoint to give an agent the catalog and the ability to run checks. The endpoint lives on the API host: https://api.arbiterqa.com/mcp

mcp.json

{
  "mcpServers": {
    "arbiterqa": {
      "url": "https://api.arbiterqa.com/mcp"
    }
  }
}

Catalog API

Public read endpoints

The catalog, per-check detail, and sets are public and require no auth — the same JSON that powers this site and the MCP get_validation tool. Running a job (which spends credits) happens on the app behind your API key.

curl

# Public, no-auth catalog reads
curl https://api.arbiterqa.com/api/validations
curl https://api.arbiterqa.com/api/validations/font-size-body-min-max
curl https://api.arbiterqa.com/api/validation-sets
curl https://api.arbiterqa.com/api/validation-sets/accessibility-compliance

For agents

Front-door files

Agents can read our capabilities directly. These stay on the API host where agents expect them.

llms.txtCompact capability index llms-full.txtFull contract and prose MCP endpointHosted tool server npm: arbiterqaThe command-line client

Get an API key

Create a free account with 1,000 credits, generate a key, and run your first check in minutes.

Start free Browse the catalog