@mcpolyglot/client

@mcpolyglot/client

Typed client for a running mcpolyglot HTTP server. Use it from scripts, backends, or tests that want policy-checked database access without an MCP host. Every call goes through the same server pipeline an agent's would: scopes, policy, redaction, rate limit, audit.

npm i @mcpolyglot/client

import { McpolyglotClient, McpolyglotDeniedError } from '@mcpolyglot/client';

const db = await McpolyglotClient.connect('http://127.0.0.1:7337/mcp', {
  token: process.env.MCPOLYGLOT_TOKEN!,
  agentId: 'billing-report', // shows up as agentId in the audit log
});

const tables = await db.listTables('bank'); // only what the policy exposes

const { rows } = await db.query<{ kind: string; balance_cents: string }>(
  'bank',
  'SELECT kind, balance_cents FROM accounts WHERE customer_id = $1',
  [1],
);

const { decision } = await db.query('bank', 'DELETE FROM accounts WHERE id = 1', [], {
  dryRun: true,
}); // { allow: false, reason: 'Table "accounts" is read-only ...', ... }

try {
  await db.query('bank', 'SELECT ssn FROM customers');
} catch (e) {
  if (e instanceof McpolyglotDeniedError) console.log(e.code, e.reason); // forbidden.policy ...
}

await db.close();

API

• McpolyglotClient.connect(url, { token, agentId? }): url is the server's /mcp endpoint.
• listTables(sourceId): TableInfo[], with hidden tables and denied columns already removed.
• query<Row>(sourceId, sql, params?, { limit?, dryRun? }): QueryResult<Row>, or DryRunResult when dryRun: true. Row is a type assertion, not a runtime check.
• McpolyglotDeniedError: thrown when the server refuses a call. code is forbidden.policy, forbidden.scope, rate_limited, or timeout; reason is the server's explanation.

Values arrive as the server serializes them. On Postgres, bigint and numeric come back as strings.

MIT licensed.