nexql-mcp

Standalone Postgres MCP server — schema-aware, read-only by default, installable everywhere.

NexQL Pro ships an in-process MCP server locked to VS Code (pro/src/mcp/). This repo extracts that capability into an independent Rust binary any MCP client can spawn: Claude Desktop, Cursor, VS Code Copilot, Zed, etc.

Status: Phases 0–6 + Phase 7 extension cutover (stdio spawn) + Phase 8 HTTP (bearer, sessions, rate limit) + Phase 9 write/admin tools landed. 54 tools across Schema, Query, Context, Perf, Write, and Admin. Full OAuth gateway stays pro-only; session-store LRU eviction cap not yet implemented. See docs/CUTOVER.md.

Why this exists

Competing Postgres MCP servers expose connect → run query → return rows. Models hallucinate table names against schemas that do not exist. NexQL's moat is the offline schema index (TF-IDF, join graph with inferred FKs, value profiles, optional embeddings, RRF fusion) built in pro/src/features/dbindex/. This repo ports that index plus 54 query/schema/DBA/meta tools from Pro into a fast, trivially installable binary.

Architecture

crates/
├── nexql-mcp/      CLI, subcommands, wiring (binary)
├── nexql-proto/    MCP JSON-RPC types, transports
├── nexql-tools/    tool registry, schemas, executors
├── nexql-index/    dbindex port (builder, store, lexical, joins, embed)
├── nexql-conn/     connection resolution, pool, credentials
└── nexql-policy/   access modes, allow/deny, PII, caps, audit
npm/                npx shim (per-platform optionalDependencies)
mcpb/               one-click Claude Desktop bundle
docs/               per-client setup, tool reference

Layering is one-directional: policy + conn are leaves → index → tools → binary. nexql-tools never depends on nexql-proto.

Scope boundary: nexql-mcp manages objects within a connected database (tables, indexes, columns, …), not the database catalog itself. CREATE DATABASE / DROP DATABASE are rejected in every access mode — permanent, intentional scope, not a gap. See docs/tools/README.md and docs/REFERENCE.md.

Install

npx — recommended, zero install

npx -y nexql-mcp@latest postgres://dev@localhost:5432/appdb doctor

-y skips the "ok to proceed?" confirmation prompt; @latest always resolves the newest published release instead of whatever npx happens to have cached — always use both together. This is the desired way to run nexql-mcp: no separate install step, nothing added to PATH, works identically whether a human is typing it or an AI agent is running it on your behalf. Requires Node.js (npx ships with it) — nothing else.

# Verify
npx -y nexql-mcp@latest --version

# Setup
npx -y nexql-mcp@latest setup  # initialize connections and db profiles

# Wire your MCP client (or run the guided wizard)
npx -y nexql-mcp@latest init cursor          # Cursor
npx -y nexql-mcp@latest init claude-desktop  # Claude Desktop
npx -y nexql-mcp@latest init vscode-copilot  # VS Code Copilot
npx -y nexql-mcp@latest tui                  # interactive profile + client wiring

Client config (command/args) uses the same pattern — no install step for the client to rely on either:

{
  "mcpServers": {
    "nexql-mcp": {
      "command": "npx",
      "args": ["-y", "nexql-mcp@latest", "--profile", "mydb"]
    }
  }
}

If you are an AI coding agent setting this up on a user's behalf: run npx -y nexql-mcp@latest init <client> --apply — non-interactive, no browser needed, writes the merged client config directly (.mcp.json for claude-code, claude_desktop_config.json for claude-desktop, etc. — see docs/clients/README.md for exact paths per client). Or drive nexql-mcp setup's HTTP API directly: POST /api/v1/clients/preview → POST /api/v1/clients/apply (bearer token printed to stderr on startup). Prefer this over hand-writing claude mcp add-style shell commands or hand-parsing/merging the client's JSON config yourself.

Per-client config paths and paste blocks: docs/clients/README.md.

npm install -g nexql-mcp also works if you'd rather have a permanent nexql-mcp on PATH than repeat npx -y nexql-mcp@latest — same shim, same @nexql/mcp-<os>-<arch> prebuilt binaries, no Rust toolchain needed either way.

Linux system requirements: prebuilt GNU/Linux binaries target glibc 2.35+ (Ubuntu 22.04, Debian 12, RHEL 9, and newer). If npx/npm fails with GLIBC_2.39 not found, use one of the fallback methods below (cargo install builds from source; Docker sidesteps glibc entirely). Musl/static Linux builds are not published yet.

Other install methods (fallback)

Reach for one of these only if npx isn't an option — an offline/air-gapped environment, a CI image that wants a pinned binary baked in, no Node.js available, or you simply prefer a permanent install. All ship the same binary as the npm package.

curl -fsSL https://raw.githubusercontent.com/NexQL-OSS/mcp/main/scripts/install.sh | bash

NEXQL_MCP_VERSION=v0.2.2 curl -fsSL https://raw.githubusercontent.com/NexQL-OSS/mcp/main/scripts/install.sh | bash

irm https://raw.githubusercontent.com/NexQL-OSS/mcp/main/scripts/install.ps1 | iex

$env:NEXQL_MCP_VERSION = "v0.2.2"; irm https://raw.githubusercontent.com/NexQL-OSS/mcp/main/scripts/install.ps1 | iex

curl -LsSf https://astral.sh/uv/install.sh | sh   # macOS / Linux

irm https://astral.sh/uv/install.ps1 | iex        # Windows

uv tool install nexql-mcp
uv tool update-shell    # once, if uv warns the tool bin dir is not on PATH

uvx nexql-mcp postgres://dev@localhost:5432/appdb doctor

uv tool install 'nexql-mcp==0.2.2'

uv tool upgrade nexql-mcp

cargo install nexql-mcp

sudo apt install clang libclang-dev   # Debian/Ubuntu
sudo pacman -S clang                  # Arch

docker run --rm -i ghcr.io/nexql-oss/mcp:0.5.0 postgres://dev@host.docker.internal:5432/appdb
# or: ghcr.io/nexql-oss/mcp:latest

docker build -t nexql-mcp:0.5.0 .
docker run --rm -i nexql-mcp:0.5.0 postgres://dev@host.docker.internal:5432/appdb

export LIBCLANG_PATH="${LIBCLANG_PATH:-/usr/lib}"   # or your llvm lib dir
cargo build --release -p nexql-mcp
./target/release/nexql-mcp postgres://dev@localhost:5432/appdb

Set up a connection

Commands below assume nexql-mcp resolves on PATH. If you're running via npx instead, prefix each one with npx -y nexql-mcp@latest in place of nexql-mcp — see Install.

One-off, no config — pass a connection string directly:

nexql-mcp postgres://dev@localhost:5432/appdb

Saved profiles — put connections in ~/.config/nexql-mcp/config.toml (override the path with NEXQL_MCP_CONFIG):

default_profile = "local"

[profiles.local]
url = "postgres://dev@localhost:5432/appdb"
access_mode = "read"

[profiles.prod]
host = "prod.example.com"
dbname = "app"
user = "readonly_agent"
password_command = "op read op://vault/pg/password"   # never store plaintext secrets
sslmode = "verify-full"
access_mode = "read"
schemas = ["public", "billing"]
deny_tables = ["auth.*"]
pii_columns = ["public.users.ssn", "public.users.email"]
max_rows = 200

Full field reference: docs/config.example.toml. Then run bare (nexql-mcp) to use default_profile, or nexql-mcp --profile prod.

Test a connection before wiring it into a client:

nexql-mcp postgres://dev@localhost:5432/appdb doctor
# or, for a saved profile (note: --profile goes before the subcommand):
nexql-mcp --profile prod doctor

Guided setup — an interactive profile editor plus one-keystroke wiring into whichever clients you use:

• nexql-mcp tui — terminal UI (see Interactive TUI below)
• nexql-mcp setup — browser UI on loopback (profiles, client wiring, npx/path launch toggle); also npx -y nexql-mcp@latest setup

Wire a client

nexql-mcp postgres://dev@localhost:5432/appdb init cursor

Supported init clients: claude | claude-desktop | claude-code | cursor | vscode | vscode-copilot | zed | windsurf | continue | jetbrains | openai-agents.

Per-client paste blocks: docs/clients/README.md.

Tool surface / context budget

--tools query|dba|meta|full (env: NEXQL_MCP_TOOLS) restricts which tools are advertised to the client — a context-window budgeting knob, not a security boundary. It's purely advisory: nexql-policy's access_mode (read/write/admin, set via --access-mode or a profile's access_mode) is what actually gates what a call can do. Pick a narrower profile only to reduce how much tool-schema JSON gets loaded into your agent's context window:

• query — core query/discovery tools (schema search, run_select, explain_query, …)
• dba — monitoring/admin tools (health checks, index suggestions, locks, …)
• meta — the smallest initial surface, plus discover_tools for lazy on-demand activation of the rest (see docs/tools/README.md)
• full (default) — every active tool

Exact membership per profile: nexql-tools/src/registry.rs's QUERY_PROFILE/DBA_PROFILE/META_PROFILE/ACTIVE constants.

Use with the NexQL VS Code extension

If you already use ric-v.postgres-explorer (+ NexQL Pro), you don't need any of the above — the extension can spawn this binary itself and reuse your existing saved connections instead of a separate config.toml.

1. Settings → search NexQL: Mcp: Enabled (postgresExplorer.mcp.enabled) → check it. Off by default.
2. That's it — it takes effect immediately (no reload needed) and picks up every connection already saved in postgresExplorer.connections. It shows up as an MCP server named NexQL in Copilot Chat / agent-mode tool pickers.

The extension resolves the binary in this order: postgresExplorer.mcp.binaryPath setting → NEXQL_MCP_BIN env var → a copy bundled with the extension → whatever nexql-mcp is on your PATH (i.e. anything installed via npm/cargo/curl above). Set postgresExplorer.mcp.binaryPath explicitly if you want the extension to use a specific install.

Interactive TUI

nexql-mcp tui

Guided profile editor: add/edit/delete a connection profile, test-connect it live before saving, then pick any of 7 clients (Claude Desktop, Claude Code, Cursor, VS Code, Copilot Chat, Zed, Windsurf) to wire it into at once. Each selected client's real config file is read, merged (existing unrelated servers are preserved), shown as a diff, and only written after you confirm — a timestamped backup is kept alongside it. continue / jetbrains / openai-agents have no safe on-disk merge target, so those stay copy-paste snippets in the summary screen, same as init.

Keys: n new · e/Enter edit · d delete · t test · w wire into clients · q quit. Bare nexql-mcp (no URL, no flags) launches the TUI automatically when nothing else resolves a connection.

Releases

Pushing a v* tag triggers .github/workflows/release.yml: builds darwin arm64/x64, linux gnu arm64/x64, and windows x64; attaches archives, per-platform .mcpb bundles, a CycloneDX SBOM, and a rendered Homebrew formula to a GitHub release; publishes the npm packages and GHCR image; and publishes the workspace crates to crates.io in dependency order. A follow-up workflow (publish-mcp-registry.yml) then lists the release on the MCP Registry via GitHub OIDC. Linux GNU binaries are built on Ubuntu 22.04 (glibc 2.35). Musl targets remain deferred until a clang-enabled musl builder is validated.

Development

cargo check          # workspace compile
cargo run -p nexql-mcp -- doctor
cargo test -p nexql-mcp -- init_clients
cargo fmt --all
cargo clippy --workspace --all-targets

Read CLAUDE.md and docs/REFERENCE.md before implementing.

License

GPL-3.0-only for all crates in this repo, from v0.2.0 onward. If you distribute this program or a derivative — including bundled inside another application — you must release your source under the GPL as well.

Releases up to and including v0.1.6 were published under Apache-2.0. That grant is irrevocable for those versions and is unaffected by this change.

Copyright is held solely by the NexQL-OSS Team, so commercial licenses that lift the GPL obligation are available on request. Premium extensions (provider embeddings, team sync, hosted gateway) live in a separate proprietary crate.

Roadmap

Full plan: internal design doc (federated-greeting-badger). Cutover details: docs/CUTOVER.md.

Reference implementation

TypeScript sources in the sibling nexql-pro checkout (chat still uses these; MCP HTTP stack removed):

• pro/src/mcp/McpDefinitionProvider.ts — stdio spawn of this binary
• pro/src/mcp/NexqlMcpStdioHost.ts — ephemeral profile + binary resolve
• pro/src/providers/chat/tools/ToolSpec.ts
• pro/src/providers/chat/tools/ToolExecutor.ts
• pro/src/features/dbindex/*