A suite of engine-neutral developer tools for the M (MUMPS) programming language, built around a CI/CD-friendly, test-driven-development workflow. At the center sit two complementary projects: m-stdlib, a pure-M runtime standard library (assertions, fixtures, mocks, JSON, regex, HTTP, crypto, logging, …) that gives every test the primitives it needs to be expressive, isolated, and reproducible; and m-cli, the m <subcommand> command-line toolchain (m fmt, m lint, m test, m coverage, m watch, m lsp, …) that makes the red → green → refactor loop, pre-commit hooks, coverage gates, and CI pipelines a first-class experience. Together with a real parser (tree-sitter-m), a citable language reference (m-standard), a lightweight containerized test engine (m-test-engine), and editor integrations, they form an end-to-end TDD stack that works identically for InterSystems IRIS and YottaDB developers maintaining modern (pythonic) M code, as well as large legacy (VistA) M code.

m-dev-tools ships an MCP server (m-dev-tools-mcp, also listed on the official MCP registry as io.github.m-dev-tools/m-dev-tools-mcp) that exposes route_intent / describe / verify over the catalog so any MCP-capable agent (Claude Code, Codex, Continue, …) can resolve plain-English M-tooling intent without guessing. See the AI users guide for install paths (PyPI, .mcp.json, registry-driven), example sessions, and the no-MCP fallback that walks tools.json directly.

M (MUMPS) is the language supporting a great deal of healthcare and financial infrastructure worldwide, but its modern developer tooling has historically lagged behind mainstream languages. The 2026 cross-engine gap analysis (docs/history/m-tools-gap-analysis.md) inventoried the deficit — no test runner, no logic linter, no formatter, no single-test selection, no test watcher — and ranked the missing pieces into four impact tiers.

m-dev-tools is the focused remediation of that top tier: the inner development loop that mainstream language ecosystems take for granted and that M has never had. m-dev-tools also provides a portable, industry-conformant M standard library which has not existed to date, enabling rapid development of applications without re-inventing wheels.

The M test-driven-development walkthrough is an end-to-end transcript of building a small data-analysis app — reqstats, an HTTP-access-log summarizer — using only the m toolchain and m-stdlib. Exercises every m <subcommand> (fmt / lint / test / coverage / watch / lsp / new / run / build / ci) and the M standard library it consumes. The fastest way to see modern test-driven development with continuous integration on a clean host.

See the Getting started guide for prerequisites, install paths, verification, and troubleshooting.

curl -O https://raw.githubusercontent.com/m-dev-tools/.github/main/setup.sh
less ./setup.sh
bash ./setup.sh

                          ┌────────────────────────────────────┐
                          │   .github/docs/history/            │
                          │   (frozen snapshots from the       │
                          │    former m-tools seed repo)       │
                          │   • original gap analysis          │
                          │   • Tier 1–4 strategy docs         │
                          └─────────────────┬──────────────────┘
                                            │ shaped
                                            ▼
   ════════════════════════════ FOUNDATION ════════════════════════════════

   ┌────────────────────────┐                  ┌──────────────────────────┐
   │      m-standard        │  grammar-surface │      tree-sitter-m       │
   │  citable M reference   │ ───────────────▶ │   parser → AST           │
   │  ANSI ⊕ YDB ⊕ IRIS ⊕   │      .json       │   99.06 % on VistA       │
   │  VA SAC, as TSV+JSON   │                  │   WASM · JS · Rust ·     │
   └────────────┬───────────┘                  │   Python · Go bindings   │
                │ TSVs                         └──────────────┬───────────┘
                │ (commands, ISVs, functions)                 │ AST
                │                                             │
   ════════════════════════════ TOOLCHAIN ═════════════════════════════════
                │                                             │
                ▼                                             ▼
   ┌────────────────────────────────────────────────────────────────────┐
   │                              m-cli                                 │
   │   m fmt    m lint    m test    m coverage    m watch    m lsp      │
   │   m doc    m new     m run     m build       m doctor   m ci       │
   └────┬─────────────────┬─────────────────────────────┬────────────────┘
        │ entry-points    │ docker exec                 │ manifest
        ▼                 ▼                             ▼
   ┌──────────────┐  ┌──────────────────┐  ┌─────────────────────────────┐
   │ m-cli-extras │  │  m-test-engine   │  │          m-stdlib           │
   │ out-of-tree  │  │ minimal YDB      │  │ pure-M runtime — STDJSON,   │
   │ plugins      │  │ Docker container │◀─│ STDREGEX, STDHTTP, STDFS,   │
   │ (corpus-     │  │ (`docker exec`,  │  │ STDASSERT, STDFIX, STDMOCK, │
   │ stats, …)    │  │  /work mount)    │  │ STDCRYPTO, STDLOG, … 32 mods│
   └──────────────┘  └──────────────────┘  └───────────────┬─────────────┘
                                                           │ stdlib-manifest.json
   ════════════════════════════ EDITORS ═══════════════════════════════════
                                                           │
   ┌──────────────────────────────┐         ┌──────────────▼───────────────┐
   │   tree-sitter-m-vscode       │         │      m-stdlib-vscode         │
   │ • WASM syntax highlighting   │         │ • hover docs                 │
   │ • spawns `m lsp` for live    │         │ • goto-definition            │
   │   diagnostics + Quick Fix    │         │ • completion for STD*        │
   │ • workspace smoke-report     │         │   symbols in .m files        │
   └──────────────────────┬───────┘         └──────────────────────────────┘
                          │ uses tree-sitter-m WASM
                          ▼
   ════════════════════════════ VALIDATION ════════════════════════════════

   ┌──────────────────────────────────────────────────────────────────────┐
   │                          m-modern-corpus                             │
   │  Snapshots of modern non-VistA M (EWD, mgsql, YDBOcto aux, YDBTest)  │
   │  — calibrates the parser's grammar gates and m-cli's M-MOD-NN rules  │
   │  against contemporary idioms rather than legacy VA conventions.      │
   └──────────────────────────────────────────────────────────────────────┘

Reading the diagram from the top:

1. m-standard reconciles four authoritative M sources (the ANSI standard, YottaDB's docs, InterSystems IRIS's docs, and the VA SAC / XINDEX rule set) into a single citable reference. It emits grammar-surface.json and a family of TSVs.
2. tree-sitter-m is generated from m-standard's grammar surface — one coupling point, pinned by schema_version — so the parser stays honest to the published reference.
3. m-cli consumes both: the parser for AST-driven m fmt / m lint / m test / coverage / LSP, and the TSVs for keyword classification (every command, intrinsic function, and special variable in every profile).
4. Three things plug into m-cli: m-cli-extras via the m_cli.plugins entry-point group; m-test-engine via docker exec (m-cli's m test and m coverage shell commands at the container, which bind-mounts the consumer's source at /work); and m-stdlib via the manifest that m doc / m search / m examples / m errors read to surface the STD* public surface.
5. m-stdlib runs its own tests through the same engine — m-test-engine is the shared YottaDB substrate for both the toolchain and the runtime library, so a working CI install for one project is automatically a working CI install for the other.
6. Editors layer on top. The tree-sitter-m-vscode extension renders syntax via the parser's WASM build and spawns m lsp for live diagnostics / Quick Fix / hover / completion; m-stdlib-vscode reads m-stdlib's manifest directly for STD*-specific hover, goto-def, and completion.
7. m-modern-corpus is the regression substrate for both the parser and the linter — the M-MOD-NN rule track was calibrated against this corpus so m lint --rules=default produces ~3 findings per routine on modern code rather than the ~57 the legacy XINDEX rules emit.

Most repos are AGPL-3.0, the two VS Code extensions are MIT to align with the broader extension ecosystem, and m-modern-corpus carries per-subdirectory upstream licenses (see its LICENSES.md). A migrated repo's license is the canonical statement; this README is summary only.

Maintainers and tool authors working on:

• IRIS ObjectScript / Caché-derived M codebases (cooperative scope — IRIS extensions are documented as iris-extension, not "ANSI")
• YottaDB — the open-source M engine; default test target
• General-purpose M libraries that aim to work on either engine
• Editor and AI-assistant integrations that need a real M parser

VistA-specific code, FileMan, RPC infrastructure, and KIDS tooling live in separate repositories under a different organization. m-dev-tools is explicitly the engine-neutral, modern-M half of the ecosystem.