Ai Quality Gate MCP Server

AI Quality Gate

MCP Server for AI code quality automation.

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What It Does

AI writes code → calls quality_fix → Server fixes what it can → Reports remaining issues to AI.

Hybrid Approach:

• Phase 1: ESLint + 627 rules + Prettier (~2-8s, always runs)
• Phase 2: SonarQube Server (~30-60s, optional)

Important: ESLint vs Prettier

ESLint rules are controlled by MCP for consistent quality gates. Prettier uses project's config so formatting matches project preferences.

Phase 1 Rule Coverage:

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Installation

Prerequisites

• Node.js 18+ on your PATH (node -v).
• Cursor, Antigravity, OpenCode (or another MCP-capable editor) with MCP enabled.

Project root is auto-detected when PROJECT_ROOT is omitted: the server walks up from the MCP process working directory until it finds package.json or tsconfig.json. Set PROJECT_ROOT in env only to analyze a different tree than the inferred root.

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MCP configuration (Cursor)

Open Settings → Tools & MCP → Edit (user mcp.json). Add one server block; the examples below match .cursor/mcp.json.example (JSONC with comments — if your editor rejects comments, copy the JSON blocks below only).

Server name vs tool name: The key under mcpServers (e.g. "ai-quality-gate") is only the label for that connection in Cursor. The MCP tool your agent calls is always quality_fix — that name is fixed by this package and is separate from the server key and from ai-quality-gate.

A) Recommended: npx (no global install)

Always runs the published package; good for teams and CI-like setups.

{
  "mcpServers": {
    "ai-quality-gate": {
      "command": "npx",
      "args": ["-y", "ai-quality-gate"]
    }
  }
}

B) Optional: global npm install

After npm i -g ai-quality-gate, the ai-quality-gate binary is on your PATH:

{
  "mcpServers": {
    "ai-quality-gate": {
      "command": "ai-quality-gate",
      "args": []
    }
  }
}

C) SonarQube (Phase 2)

Requires a running SonarQube instance, sonar-scanner available (see SonarQube Setup), and all three variables below. Phase 1 still runs first.

{
  "mcpServers": {
    "ai-quality-gate": {
      "command": "npx",
      "args": ["-y", "ai-quality-gate"],
      "env": {
        "SONAR_HOST_URL": "http://localhost:9000",
        "SONAR_TOKEN": "your_sonar_token",
        "SONAR_PROJECT_KEY": "your_project_key"
      }
    }
  }
}

D) Optional environment variables (any server)

Add an "env" object when you need overrides. Merge order for config is defaults → .quality-gate.yaml / .quality-gate.json → environment variables.

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MCP configuration

Cursor, Antigravity, etc..

{
  "mcpServers": {
    "ai-quality-gate": {
      "command": "npx",
      "args": ["-y", "ai-quality-gate"]
    }
  }
}

(OpenCode)

Create or edit OpenCode config (typically ~/.config/opencode/opencode.json or project-level config):

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "ai-quality-gate": {
      "type": "local",
      "enabled": true,
      "command": ["npx", "-y", "ai-quality-gate"]
    }
  }
}

Environment variables can be added under the server config if needed (see C) SonarQube (Phase 2) above).

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Local development (this repository)

To dogfood or contribute:

1. yarn build — generates dist/server.js.
2. Point MCP at the built file (absolute paths):

{
  "mcpServers": {
    "ai-quality-gate-dev": {
      "command": "node",
      "args": ["/ABSOLUTE/PATH/TO/ai-quality-gate/dist/server.js"]
    }
  }
}

1. Reload MCP. Use env.PROJECT_ROOT only if the repo you analyze differs from the inferred root.

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2. Add AI Rule

Settings → Rules and Commands → Add Rule:

After every code change, before telling the user "done",
AI must call the quality_fix MCP tool. This is mandatory.

3. Use It

AI writes code → calls quality_fix → Fixes errors → "Done ✅"

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CLI: interactive config (--setup)

The interactive wizard creates or updates .quality-gate.yaml without hand-editing: it walks you through project root, optional SonarQube (host URL + project key; token is not saved to disk — use SONAR_TOKEN in your environment), which Phase 1 tools to enable (ESLint, curly-brace / arrow AST fixers, Prettier, JSON validator), timeouts, and i18n rules. The generated file includes a fixers: block you can adjust later.

After yarn build (or install from npm), run from the target project (or any path under it):

node dist/server.js --setup

PROJECT_ROOT is inferred when unset (see MCP configuration). Use the same entrypoint as the MCP server (node dist/server.js or npx ai-quality-gate); only the --setup flag switches to wizard mode. Answer prompts in the terminal; on success you get a ready-to-use config next to your project root.

Other CLI modes: --check (read-only Phase 1), --fix (default behavior when using CLI quality run), --phase1-only, --phase2-only — see docs/DEVELOPMENT.md.

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Optional: SonarQube Server (Phase 2)

Configure Sonar env in MCP as in C) SonarQube (Phase 2) above, or copy from .cursor/mcp.json.example. You need sonar-scanner on your machine for analysis (see below).

SonarQube Setup

Docker (Recommended)

# Start SonarQube
docker run -d --name sonarqube -p 9000:9000 sonarqube:community

# First login: admin/admin → change password
# http://localhost:9000

Docker Compose

# docker-compose.yml
version: '3'
services:
  sonarqube:
    image: sonarqube:community
    ports:
      - '9000:9000'
    volumes:
      - sonarqube_data:/opt/sonarqube/data
      - sonarqube_logs:/opt/sonarqube/logs
      - sonarqube_extensions:/opt/sonarqube/extensions

volumes:
  sonarqube_data:
  sonarqube_logs:
  sonarqube_extensions:

docker-compose up -d

Creating SonarQube Token

1. http://localhost:9000 → Login (admin)
2. My Account → Security → Generate Tokens
3. Select token type: Global Analysis Token
4. Copy token → use as SONAR_TOKEN

Installing sonar-scanner

For custom path: SONAR_SCANNER_PATH env var

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Configuration

Optional files (discovered by walking up from the inferred project root — same algorithm as package.json / tsconfig.json — or from PROJECT_ROOT when set): .quality-gate.yaml (preferred) or .quality-gate.json. Same fields as environment variables (camelCase); you may nest Sonar settings under sonar: { hostUrl, token, projectKey, scannerPath }.

Merge order: defaults → config file → environment variables (ENV wins on conflicts).

Set QUALITY_GATE_CONFIG to an explicit path to skip discovery.

Custom rules (customRules)

Optional line-based regex checks on lintable files (Phase 1). Each match is reported as an issue with rule set to custom:<id> (and included in quality_fix remaining). Example:

customRules:
  - id: no-console
    message: 'Console.log is not allowed'
    pattern: 'console\\.log\\('
    severity: error
  - id: no-debugger
    message: 'Debugger statement found'
    pattern: 'debugger'
    severity: warning

Patterns use JavaScript RegExp source (escape backslashes as in YAML strings). Invalid patterns are skipped at runtime with a log line.

JSON validator & i18n locale files

When fixers.jsonValidator is enabled and you pass JSON paths that match locale patterns (for example locales/en.json / locales/tr.json), the tool compares keys across those files.

• Syntax errors, invalid UTF-8 BOM, etc. → reported as issues and fail Phase 1 / quality_fix until fixed.
• Missing or extra keys between locale files → collected as i18nIssues in the validator result and printed as warnings on stderr during Phase 1. They do not set passed: false and do not block the gate.

Treat i18nIssues as advisory unless you add your own CI check on top.

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Environment Variables

All variables are optional unless you use Phase 2, which requires SONAR_HOST_URL, SONAR_TOKEN, and SONAR_PROJECT_KEY together.

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Auto-Fix

Phase 1 automatically fixes these issues:

ESLint Auto-Fix (~100+ rules)

// var → const/let
var x = 1        →  const x = 1

// forEach → for...of (unicorn/no-array-for-each)
arr.forEach(x => f(x))  →  for (const x of arr) f(x)

// Nested ternary → extracted (unicorn/no-nested-ternary)
a ? b : c ? d : e  →  const temp = c ? d : e; a ? b : temp

// Unused imports removed
import { unused } from 'x'  →  (removed)

// Type imports (consistent-type-imports)
import { Type } from 'x'  →  import type { Type } from 'x'

// Optional chain (prefer-optional-chain)
a && a.b && a.b.c  →  a?.b?.c

// Regex optimization (regexp/*)
/[0-9]/  →  /\d/

AST Auto-Fix

// Remove unnecessary curly braces (single-line if)
if (x) { return true }  →  if (x) return true

Prettier Formatting

After ESLint fixes, Prettier runs to ensure consistent formatting:

// ESLint removes braces but leaves awkward format:
if (x) return true

// Prettier fixes to single line:
if (x) return true

Note: Prettier uses project's config, not MCP's.

Everything else: Reported to AI, AI fixes it.

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API

Tool: quality_fix

// Input
{
  files: string[] // File paths to check
}

// Output
{
  phase: "local" | "server" | "complete",
  success: boolean,
  message: string,
  fixed: {
    eslint: number,          // ESLint auto-fixes
    curlyBraces: number,   // AST: single-statement if braces
    singleLineArrow: number, // AST: arrow body style
    prettier: number,      // Prettier formatting
    json: number           // JSON validation passes counted
  },
  remaining: Issue[],
  timing: {
    phase1: string,
    phase2?: string,
    total: string
  }
}

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Feature Flags

ENABLE_I18N_RULES

For projects with internationalization (i18n), enable literal string detection:

{
  "env": {
    "ENABLE_I18N_RULES": "true"
  }
}

When enabled:

// ⚠️ Warning
<h1>Hello World</h1>

// ✅ OK
<h1>{t('hello')}</h1>

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Troubleshooting

MCP: quality_fix does not appear

1. Node.js 18+ — run node -v and npx --version.
2. Reload Cursor after editing mcp.json (or use the MCP refresh control).
3. JSON — the file must be valid JSON (no trailing commas). Copy from the MCP configuration section if unsure.
4. Global install — if you use "command": "ai-quality-gate", run npm i -g ai-quality-gate once so the binary exists.

Windows

"npx not found" error:

# Node.js must be in PATH
# Check in PowerShell:
where.exe npx

Permission denied:

# Run PowerShell as Administrator

macOS / Linux

"Permission denied" error:

# Fix npm global directory
mkdir ~/.npm-global
npm config set prefix '~/.npm-global'
echo 'export PATH=~/.npm-global/bin:$PATH' >> ~/.zshrc
source ~/.zshrc

"sonar-scanner not found" error:

# Install via Homebrew
brew install sonar-scanner

# Or via npm
npm install -g sonarqube-scanner

SonarQube

"Insufficient privileges" error:

• SonarQube → Administration → Security → Global Permissions
• Give Anyone group Browse and Execute Analysis permissions

"Project not found" error:

• Create project manually for first analysis: Projects → Create Project → Manually

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Clone & build (contributors)

git clone https://github.com/mustafacagri/ai-quality-gate.git
cd ai-quality-gate
yarn install
yarn build

Use Local development (this repository) for MCP pointing at dist/server.js.

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Docs

• SETUP.md — Local setup (if included in your tree)
• AGREEMENTS.md, docs/ARCHITECTURE.md, etc. — optional; some files may be omitted in minimal clones. README + .cursor/mcp.json.example are enough to run the published package.

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Principles

• ✅ 627 ESLint rules (SonarJS, Unicorn, TypeScript-ESLint, etc.)
• ✅ Prettier integration (uses project's config)
• ✅ AST-based transforms (no regex)
• ✅ Verify after each fix
• ✅ Rollback on error
• ✅ ESLint config discovery (uses project config if available, otherwise embedded)
• ✅ Zero workaround
• ✅ Principal level

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License

MIT © Mustafa Çağrı Güven

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v0.0.1 — Initial release! MCP quality_fix, Phase 1/2 pipeline, CLI, config files, custom rules (see CHANGELOG)