PlainQuery | MCP DB Agent

Name: PlainQuery | MCP DB Agent
Author: Jarvis-27

by Jarvis-27version 1.0.1i★ –iRuns in the cloud

Registry nameio.github.Jarvis-27/mcp-db-agent

Install

Overview

Description from the maker (original English)

Query PostgreSQL databases in plain English — LLM-generated, safety-validated SQL.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiVery new★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs in the cloud
Transport: Streamable HTTP
Category: Databases & datasets
You need to fill in: X-API-Key

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on the maker’s server: what you ask it goes through their server.
You fill in yourself: X-API-Key

Values marked secret are keys to your account. Never share them or paste them into a chat.

You need

Runs in the cloudNothing to install; it connects over the internet

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

This address needs a key in a request header, which the add-connector menu cannot set. Use Claude Code, Cursor or VS Code instead.

Run this in your terminal

claude mcp add --transport http db-agent https://plainquery.in/mcp/ --header 'X-API-Key: your-value'

Fill in the empty values before running it.

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "db-agent": {
      "url": "https://plainquery.in/mcp/",
      "headers": {
        "X-API-Key": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "db-agent": {
      "type": "http",
      "url": "https://plainquery.in/mcp/",
      "headers": {
        "X-API-Key": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This address needs a key in a request header, which the add-connector menu cannot set. Use Claude Code, Cursor or VS Code instead.

Your choice stays on this device in a cookie; no account needed.

Values you fill in

X-API-Key secret required HTTP header
API key from POST /api/v1/users/register

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

We have not read this server’s tool list yet; we check endpoints in rotation.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 9, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account Jarvis-27, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
… Not checked yet
Endpoint responds
Not checked yet; we check endpoints in rotation
… Not checked yet
Sign-in with OAuth
Not checked yet; we check endpoints in rotation
… Not checked yet
No hidden instructions in tool descriptions
Not checked yet; we read the tool list when we check the endpoint

Compared with others in Databases & datasetsi

More stars than 0% of the other 1155 servers in this category
Published to the registry more recently than 11% of the other 1155 servers in this category
Basic checks equal to or better than 100% of the other 1155 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is PlainQuery | MCP DB Agent safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

You need to fill in: X-API-Key

Does it run on my computer or in the cloud?

It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.

Is it still maintained?

The GitHub repo last changed –, and the latest version (1.0.1) reached the registry 6 months ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT in developer mode.

What can I use instead?

In the same category: Supabase, MongoDB MCP Server, Elasticsearch MCP Server

Alternatives

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Reading a card:↓ Downloads per weeki★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

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by supabaseWidely used↓ 235.4K/wk★ 3KUpdated 3 days ago

Computer or cloud✓ supabase.com

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Elasticsearch MCP Server

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README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

PlainQuery

Ask your database questions in plain English. PlainQuery connects PostgreSQL databases to Claude, Cursor, or VS Code — and answers with real, structured data instead of guesses.

What it does

You connect a database once. Then, from any MCP client, you ask questions like:

_"How many orders did we ship in March?"_

_"Which 5 customers spent the most last year?"_

_"What's the average order value by month?"_

PlainQuery introspects your schema, generates SQL with an LLM, validates it for safety, runs it, and returns structured JSON. If a query fails, it reads the error and retries automatically.

Why PlainQuery

Natural language, real answers — no SQL required; results come from your actual data, not a hallucination.
Read-only and safe by design — every query is checked before it runs: writes (INSERT/UPDATE/DELETE/DDL) are blocked, dangerous functions and patterns are scanned out, and a LIMIT is injected automatically.
Self-correcting — when a generated query errors, the agent feeds the error back to the LLM and retries (up to a configurable limit).
Schema-aware — automatically introspects and caches your schema, so questions map to the right tables and columns.
Works with any MCP client — Claude Desktop, Cursor, VS Code Copilot, or anything that speaks MCP.
Secure multi-tenant hosting — database URLs and LLM keys are Fernet-encrypted at rest; user-supplied connection strings are SSRF-guarded; every request is tenant-scoped.
Hosted or self-hosted — use the managed service, or run the whole stack yourself with Docker.
Bring your own LLM — Anthropic Claude or Groq.

How it works

Your question

→ Schema introspection (reads tables/columns, cached) → SQL generation (schema + question → LLM → SQL) → Safety validation (blocks writes, scans dangerous patterns, injects LIMIT) → Execution (runs read-only, with a timeout) → Self-correction retry (on error: feed it back to the LLM, fix, re-run) → Structured JSON result

Architecture

Quick start

Option 1 — Use the hosted service (no install)

Sign up at `https://plainquery.in` and verify your email.
Connect your PostgreSQL database and create an API key.
Add the server to your MCP client (see Connect your MCP client).

That's it — start asking questions.

Option 2 — Run it yourself

See Self-hosting & local development below.

Connect your MCP client

PlainQuery is published on the official MCP Registry as io.github.Jarvis-27/mcp-db-agent, so registry-aware clients can discover it directly.

To configure a client manually, point it at the MCP endpoint and pass your API key:

"mcpServers": { "plainquery": { "url": "https://plainquery.in/mcp", "headers": { "X-API-Key": "mdbk_your_key_here" } } } }

The backend can also generate ready-to-paste config for VS Code, Cursor, and generic HTTP clients — call POST /api/v1/account/setup-payloads (see Setup payloads). MCP clients can authenticate with an OAuth 2.1 bearer token or an API key, depending on MCP_AUTH_MODE.

Self-hosting & local development

Prerequisites

Python 3.12+
uv
Node.js 20+ and pnpm for the frontend
At least one LLM API key (ANTHROPIC_API_KEY or GROQ_API_KEY)

Backend

uv sync

cp .env.example .env

Edit .env with at least:

CREDENTIAL_ENCRYPTION_KEYS
REGISTRATION_OPEN=true
one LLM provider key plus LLM_PROVIDER

Run the backend:

uv run uvicorn src.app:app --reload --host 0.0.0.0 --port 8000

The backend mounts:

REST API at http://localhost:8000/api
MCP endpoint at http://localhost:8000/mcp

Frontend

cd frontend

pnpm install pnpm dev

Open http://localhost:3000, sign up, complete setup, link your OAuth identity via account settings, then connect an MCP client at http://localhost:8000/mcp. The client will complete the OAuth flow automatically, or you can use an API key in api_key_only / hybrid mode.

Runtime model

Backend API: FastAPI/Starlette at src.app:app
Frontend: Next.js app in frontend/
Auth: passwordless email verification and login links
MCP auth: OAuth 2.1 bearer tokens (oauth_only), API keys (api_key_only), or both (hybrid) — set via MCP_AUTH_MODE
Setup payloads: POST /api/v1/account/setup-payloads
Billing: Stripe Checkout, Customer Portal, and webhook-confirmed Free/Pro entitlements

The product model is single-account and user-scoped: signup → verify email → connect database → link OAuth identity → use /mcp → upgrade with Stripe

Security

User-supplied database URLs are validated against SSRF, path traversal, private IPs, and DNS rebinding before any connection attempt.
Database URLs and LLM keys are Fernet-encrypted at rest, with support for key rotation.
Generated SQL is validated before execution: single-statement guard, forbidden-function scan, dangerous-pattern scan, write/DDL block, table-existence check, and automatic LIMIT injection.
Per-request context scoping prevents cross-tenant data leaks.
Per-user rate limits and fallback-LLM quotas limit cost abuse.

Important environment variables

Variable	Description
`AUTH_DATABASE_URL`	Auth/account database used by the hosted product
`CREDENTIAL_ENCRYPTION_KEYS`	Encrypts stored database URLs and other secrets
`REGISTRATION_OPEN`	Enables or disables public signup
`ANTHROPIC_API_KEY` / `GROQ_API_KEY`	LLM credentials for SQL generation
`LLM_PROVIDER`	Active provider name
`APP_BASE_URL`	Base URL used in setup payloads
`FRONTEND_BASE_URL`	Base URL used in email links
`STRIPE_SECRET_KEY` / `STRIPE_WEBHOOK_SECRET`	Stripe API and webhook credentials
`STRIPE_PRO_PRICE_ID`	Stripe Price ID that maps to the Pro plan
`STRIPE_CHECKOUT_SUCCESS_URL` / `STRIPE_CHECKOUT_CANCEL_URL`	Optional Checkout redirect overrides
`STRIPE_CUSTOMER_PORTAL_RETURN_URL`	Optional Customer Portal return URL override

See .env.example for the current full set.

API surface

Auth

POST /api/v1/auth/signup
GET /api/v1/auth/verify-email
POST /api/v1/auth/request-login-link
GET /api/v1/auth/exchange-login-link
POST /api/v1/auth/logout

Account (session-authenticated)

All account routes use session token auth (x-session-token: or Authorization: Bearer ):

GET /api/v1/account
GET /api/v1/account/status
PUT /api/v1/account/database
GET /api/v1/account/api-keys
POST /api/v1/account/api-keys
DELETE /api/v1/account/api-keys/{id}
POST /api/v1/account/api-keys/{id}/rotate
POST /api/v1/account/setup-payloads
GET /api/v1/account/dashboard
GET /api/v1/account/usage/recent

Billing

GET /api/v1/account/billing
POST /api/v1/account/billing/checkout-session
POST /api/v1/account/billing/portal-session
POST /api/v1/billing/webhook

Stripe webhooks are the source of truth for plan transitions. Checkout or subscription activation moves a user to plan_code=pro; canceled, unpaid, or past-due states restrict paid entitlements without deleting database setup.

OAuth MCP account linking (session-authenticated)

GET /api/v1/account/mcp-oauth/status
POST /api/v1/account/mcp-oauth/start
GET /api/v1/account/mcp-oauth/callback
DELETE /api/v1/account/mcp-oauth/link

MCP

POST /mcp
Auth: OAuth 2.1 bearer token, API key, or both — controlled by MCP_AUTH_MODE

Setup payloads

POST /api/v1/account/setup-payloads returns client configuration material for VS Code, Cursor, generic HTTP MCP clients, and the current ChatGPT placeholder.

curl -X POST http://localhost:8000/api/v1/account/setup-payloads \

-H "Authorization: Bearer " \ -H "Content-Type: application/json" \ -d '{"raw_api_key":"mdbk_..."}'

The backend never stores raw API keys after creation. A raw key is only embedded in setup payloads when you explicitly send it in the request.

Tests

uv run pytest tests/ -m "not integration"

uv run pytest tests/ -m integration uv run ruff check . uv run mypy src --ignore-missing-imports

Deployment smoke test

After each hosted deploy, verify the public MCP OAuth discovery surface:

uv run python scripts/smoke_mcp_deployment.py \

--mcp-url https://mcp.example.com/mcp \ --issuer-url https://YOUR_DOMAIN.auth0.com/

The smoke test checks the unauthenticated /mcp challenge, protected resource metadata, ChatGPT/Claude well-known discovery routes, and issuer metadata. To also verify authenticated MCP initialize, tools/list, and resources/list, pass a linked user's access token with --access-token or MCP_SMOKE_ACCESS_TOKEN.

Docker

Run the hosted HTTP stack:

docker compose up --build

The container image serves only the hosted HTTP runtime. The MCP endpoint remains http://localhost:8000/mcp.

PlainQuery | MCP DB Agent

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

Values you fill in

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Databases & datasetsi

Common questions

Alternatives

Supabase

MongoDB MCP Server

Elasticsearch MCP Server

README from the maker

PlainQuery

What it does

Why PlainQuery

How it works

Architecture

Quick start

Option 1 — Use the hosted service (no install)

Option 2 — Run it yourself

Connect your MCP client

Self-hosting & local development

Prerequisites

Backend

Frontend

Runtime model

Security

Important environment variables

API surface

Auth

Account (session-authenticated)

Billing

OAuth MCP account linking (session-authenticated)

MCP

Setup payloads

Tests

Deployment smoke test

Docker

License