# Agent rules for dbmole-mcp

Applies to every change in this repo, by any agent or human.

## Code style

- 4-space indentation
- No semicolons where possible (`semicolons: asNeeded`)
- Single quotes where possible
- Functions as `const fn = () => {}` where possible
- No trailing commas before a closing `}`, `]`, `)` (`trailingCommas: none`)
- Biome enforces all of the above — run `npm run lint:fix` before every commit
- Line width 100

## TypeScript discipline

- No `as unknown as X` double-casts anywhere
- No `@ts-ignore` / `@ts-expect-error` / `any` in `src/`
- In tests prefer typed fakes (see `test/unit/helpers.ts`); a single `as` cast is
  a last resort, only when there is genuinely no typed way
- Types must line up by construction — if they don't, fix the design, not the cast

## Testing

- TDD: write the failing test first, watch it fail, implement, watch it pass
- Full coverage: unit tests (mocked IO) + integration tests via testcontainers
- Coverage thresholds ≥90% lines/functions on the unit project — never lower them
- `npm run test:unit` (fast), `npm run test:int` (needs Docker)

## Commits

- Conventional Commits: `<type>(<scope>): <imperative summary>`
- Subject ≤50 chars (hard cap 72), no trailing period
- Body only when the *why* is not obvious from the diff; wrap at 72
- NO AI attribution: no `Co-Authored-By: Claude ...`, no "Generated with ..."
- No emoji

## Project constraints

- stdout is the MCP protocol channel — diagnostics go to `console.error` ONLY,
  never `console.log`
- ESM with NodeNext resolution: relative imports need the `.js` extension
- MCP SDK v1 (`@modelcontextprotocol/sdk`): `registerTool` takes a ZodRawShape
  (plain object of zod fields), NOT `z.object()`; subpath imports
  (`server/mcp.js`, `server/stdio.js`, `client/index.js`, `inMemory.js`, `types.js`)
- zod 3 (`import * as z from 'zod'`)