Mssql Mcp Core

Shared core library for the MSSQL MCP tiered package family. This package provides every tool class, the MCP server harness, environment management, audit logging, secret resolution, intent routing, and policy enforcement middleware. Consumer packages (reader, writer, server) depend on this library and call startMcpServer() with a tier to get a fully configured MCP server.

Architecture

@connorbritain/mssql-mcp-core
        |
        |-- @connorbritain/mssql-mcp-reader  (14 read-only tools)
        |-- @connorbritain/mssql-mcp-writer  (17 tools: reader + INSERT/UPDATE/DELETE)
        |-- @connorbritain/mssql-mcp-server  (20 tools: writer + CREATE TABLE/INDEX, DROP TABLE)

Each consumer package is a thin wrapper that passes its tier to startMcpServer(). All business logic, tool implementations, and governance infrastructure live here.

How Consumer Packages Use This Library

import { startMcpServer } from "@connorbritain/mssql-mcp-core";

startMcpServer({ tier: "reader" });

The tier parameter controls which tools are registered with the MCP server:

Tier	Tools	What it adds
reader	14	All read-only and schema discovery tools
writer	17	Reader tools + insert_data, update_data, delete_data
admin	20	Writer tools + create_table, create_index, drop_table

Config Builder — Visual wizard to generate configuration files for consumer packages.

Exports

Server Entry Point

import { startMcpServer } from "@connorbritain/mssql-mcp-core";

• startMcpServer(config: McpServerConfig) — Initializes the MCP server over stdio for the given tier. Registers tools, applies wrapToolRun policy middleware to each, and starts listening.

Tool Classes

All 20 tool classes are exported individually:

import {
  // Read-only (Reader tier)
  ReadDataTool,
  ListTableTool,
  ListDatabasesTool,
  ListEnvironmentsTool,
  ValidateEnvironmentConfigTool,
  ListScriptsTool,
  RunScriptTool,
  DescribeTableTool,
  SearchSchemaTool,
  ProfileTableTool,
  RelationshipInspectorTool,
  InspectDependenciesTool,
  TestConnectionTool,
  ExplainQueryTool,

  // Write (Writer tier adds these)
  InsertDataTool,
  DeleteDataTool,
  UpdateDataTool,

  // Admin/DDL (Server tier adds these)
  CreateTableTool,
  CreateIndexTool,
  DropTableTool,
} from "@connorbritain/mssql-mcp-core";

Each tool class implements the RunnableTool interface with name, description, inputSchema, and run(params).

Environment Management

import { EnvironmentManager, getEnvironmentManager } from "@connorbritain/mssql-mcp-core";

• EnvironmentManager — Manages multi-environment configurations, connection pools, per-environment policies (readonly, allowedTools, deniedTools, maxRowsDefault, requireApproval, auditLevel, allowedSchemas, deniedSchemas), and secret resolution.
• getEnvironmentManager() — Returns the singleton instance.

Audit Logging

import { AuditLogger, auditLogger } from "@connorbritain/mssql-mcp-core";

• AuditLogger — Writes JSON Lines audit log entries with timestamps, tool names, arguments (sensitive fields auto-redacted), results, session ID, and environment name.
• auditLogger — Singleton instance. Configured via AUDIT_LOG_PATH and AUDIT_LOGGING environment variables.

Secret Resolution

import {
  SecretResolver,
  createSecretResolver,
  validateDotenvPath,
  validateFileDirectory,
} from "@connorbritain/mssql-mcp-core";

• SecretResolver — Resolves ${secret:NAME} placeholders in environment config values from environment variables, .env files, or external secret providers.
• createSecretResolver(config) — Factory for SecretResolver instances.

Intent Routing

import { IntentRouter } from "@connorbritain/mssql-mcp-core";

• IntentRouter — Routes natural language intents to the appropriate MCP tool using keyword matching and scoring. Used internally by startMcpServer.

Policy Middleware

import { wrapToolRun } from "@connorbritain/mssql-mcp-core";

• wrapToolRun(tool, options) — Monkey-patches a tool's run() method to enforce per-environment policies (readonly, allowedTools, deniedTools, requireApproval), obtain a connection pool, inject environment context into tool arguments, and log all invocations to the audit logger.

Toolset Helpers

import {
  createAllToolInstances,
  getReaderTools,
  getWriterTools,
  getAdminTools,
  buildToolRegistry,
  READER_MUTATING_TOOLS,
  WRITER_MUTATING_TOOLS,
  ADMIN_MUTATING_TOOLS,
  READER_APPROVAL_EXEMPT,
  WRITER_APPROVAL_EXEMPT,
  ADMIN_APPROVAL_EXEMPT,
} from "@connorbritain/mssql-mcp-core";

• createAllToolInstances() — Instantiates all 20 tool classes and returns them as a named object.
• getReaderTools(t) — Returns the 14-tool array for the reader tier.
• getWriterTools(t) — Returns the 17-tool array for the writer tier.
• getAdminTools(t) — Returns the 20-tool array for the admin/server tier.
• buildToolRegistry(t) — Returns the full routing config array used by IntentRouter.
• READER_MUTATING_TOOLS — Empty Set<string> (reader has no mutating tools).
• WRITER_MUTATING_TOOLS — Set of insert_data, delete_data, update_data.
• ADMIN_MUTATING_TOOLS — Set of all write + DDL tool names.
• READER_APPROVAL_EXEMPT — Set of tools that bypass requireApproval in the reader tier.
• WRITER_APPROVAL_EXEMPT — Set of tools that bypass requireApproval in the writer tier.
• ADMIN_APPROVAL_EXEMPT — Set of tools that bypass requireApproval in the admin tier.

Types

import type {
  TierLevel,
  McpServerConfig,
  IntentCategory,
  RunnableTool,
  ToolRoutingConfig,
  IntentRouterOptions,
  RoutingCandidate,
  RouteParams,
  RouteResult,
  WrapToolRunOptions,
  EnvironmentConfig,
  EnvironmentsConfig,
  AccessLevel,
  AuditLogEntry,
  AuditLevel,
  SecretsConfig,
  SecretProviderConfig,
} from "@connorbritain/mssql-mcp-core";

Build

npm install
npm run build   # Compiles TypeScript to dist/
npm run watch   # Watch mode for development

Related Packages

Package	npm	Tier
Reader	@connorbritain/mssql-mcp-reader	Read-only
Writer	@connorbritain/mssql-mcp-writer	Read + write
Server	@connorbritain/mssql-mcp-server	Full admin

License

MIT