Isthmus MCP Server

Isthmus is a local [MCP](https://modelcontextprotocol.io) server that gives AI models safe, read-only access to your PostgreSQL database. One binary

Local serverstdioGo

What is the Isthmus MCP server?

Isthmus MCP server is a locally run integration for AI assistants that speak the Model Context Protocol. Isthmus is a local MCP server that gives AI models safe, read-only access to your PostgreSQL database. One binary, runs on your machine, credentials never leave.

What you get

  • Schema discovery — — explore schemas, tables, columns, foreign keys, and indexes (docs)
  • Read-only queries — — execute SQL with server-side row limits and query timeouts (docs)
  • Column masking — — protect PII with per-column redact, hash, partial, or null masks — enforced server-side (docs)
  • Policy engine — — enrich your schema with business context so the AI writes better SQL (docs)
  • SQL validation — — AST-level whitelist via pg_query parser — only SELECT and EXPLAIN allowed (docs)
  • HTTP transport — — serve MCP over HTTP for web-based clients, ChatGPT Desktop, and remote access (docs)

What the assistant can call

Once Isthmus is connected, these are the calls the assistant has available:

  • list_schemas — Discover available database schemas
  • list_tables — Tables with row counts, sizes, and descriptions
  • describe_table — Columns, types, keys, indexes, and statistics
  • profile_table — Deep analysis: sample rows, disk usage, inferred relationships
  • query — Execute read-only SQL, results as JSON
  • explain_query — PostgreSQL execution plans with optional ANALYZE

Configuration and credentials

You will need one environment variable: DATABASE_URL. The server will not start without them, which is usually why the tools fail to appear on a first run. Keep credentials in your client's env block or a secrets manager rather than in a file you might commit.

Setting it up

Setup follows the usual MCP pattern — install or clone the server, register it in your client's configuration file, restart the client. The configuration blocks on this page cover the common clients.

Choosing this one

This sits in the database access group, where several servers overlap in what they claim to do but differ sharply once you actually set them up. Isthmus's toolset — list_schemas, list_tables, describe_table and 3 more — is a fair guide to whether it matches your workflow. It is maintained by guillermoballester; worth a glance at recent repository activity before you build anything load-bearing on it.

This entry was verified against Isthmus's own documentation before publication; SyncDev keeps the directory reviewed rather than auto-generated.

Before you rely on it

  • It runs with your machine's permissions. That is convenient and also the reason to think about what you point it at before you approve a tool call.
  • Missing credentials fail quietly in some clients — if no tools show up, check the environment block first.
  • MCP clients confirm each tool call by default. Leave that on until you have watched what the isthmus mcp server does with a few real requests.

Available tools

ToolWhat it does
list_schemasDiscover available database schemas
list_tablesTables with row counts, sizes, and descriptions
describe_tableColumns, types, keys, indexes, and statistics
profile_tableDeep analysis: sample rows, disk usage, inferred relationships
queryExecute read-only SQL, results as JSON
explain_queryPostgreSQL execution plans with optional ANALYZE

How to install the Isthmus MCP server

```json
{
  "mcpServers": {
    "isthmus": {
      "command": "isthmus",
      "env": {
        "DATABASE_URL": "postgres://user:pass@localhost:5432/mydb"
      }
    }
  }
}

Configuration as documented by the project. Restart the client after saving.

Configuration

VariableDescriptionRequired
DATABASE_URLEndpoint or connection string the server talks to.Yes

Example prompts to try

  • Use Isthmus to list schemas.
  • Use Isthmus to list tables.
  • Use Isthmus to describe table.

Frequently asked questions

It connects Isthmus to MCP-compatible AI assistants such as Claude and Cursor, exposing 6 tools (list_schemas, list_tables, describe_table, and more) that the assistant can call on your behalf. Instead of copying data back and forth by hand, the assistant works with Isthmus directly.