Postgres MCP: SSL connection required by Supabase, Neon or RDS (add sslmode=require)

TL;DR: Managed Postgres providers (Supabase, Neon, RDS) require TLS and your MCP server is connecting without it. Append ?sslmode=require to the connection URL in your client config. That is the whole fix.

Error: SSL connection is required. Please specify SSL options and retry.

Variant phrasings you may see: SSL is required, server requires encryption, no pg_hba.conf entry for host ... SSL off.

Fix it

1. Find the connection URL in your MCP client config (env block, e.g. DATABASE_URL or the server's first CLI arg).
2. Append the SSL mode parameter:

postgresql://db.supabase.co:5432/postgres?sslmode=require

If the URL already has query parameters, join with & instead: ...?connect_timeout=10&sslmode=require.

3. Restart the MCP client so the server picks up the new URL.

   Expected: the next tool call connects and returns rows. No SSL error.

When to use this

• Connecting an MCP Postgres server to Supabase, Neon, RDS, or any managed Postgres.
• The error mentions SSL, TLS, or encryption being required.

When NOT to use this

• Local dev Postgres (Docker, Homebrew). Forcing SSL there causes the opposite error. Use sslmode=disable for local dev if needed.
• The error is a certificate verification failure (self-signed certificate). That needs the CA cert or a different sslmode, not just require.

Compatibility

• All MCP Postgres servers that pass the URL to node-postgres/pg: @modelcontextprotocol/server-postgres, yawlabs/postgres-mcp, Tabulus, pgedge-postgres-mcp.
• Supabase, Neon, AWS RDS, Google Cloud SQL, Azure Database for PostgreSQL.

Why it happens

Managed Postgres fleets terminate plain connections as a security policy. The pg driver defaults to opportunistic SSL (prefer), which is not enough for providers that mandate it. sslmode=require tells the driver to always negotiate TLS, which is what the provider expects.

Edge cases

• Supabase pooler URLs (port 6543) also need sslmode=require.
• If you get a certificate error after adding it, your provider uses a custom CA. Either supply the CA (sslrootcert) or check the provider docs for their recommended sslmode.
• Some servers read the URL once at startup. A client restart is required, not just a new chat.

The Tabulus (WalkingMountain/tabulus) troubleshooting table documents this exact failure mode: Error ... SSL ... required with the cause managed Postgres (Supabase, Neon, RDS) requires TLS and the fix append ?sslmode=require to the URL. This is the documented gotcha for connecting MCP Postgres servers to managed providers. Source: https://github.com/WalkingMountain/tabulus