PowerMCP connector: PLEXOSDB (plexosdb-mcp CRUD + translate-to-Sienna via r2x)

[elasticdotventures]

Summary

Add a PLEXOSDB PowerMCP connector: a thin re-export of plexosdb-mcp's own MCP server
(direct PLEXOS object/property/membership CRUD, ~28 tools) plus translate_to_sienna and
compare_solutions, calling the r2x package directly. This is the PLEXOS-side half of the
original two-format proposal — the paired SIENNA connector (solve + translate_to_plexos)
is tracked separately as #54, since the two share no PowerMCP code, only the upstream r2x
dependency each calls directly (the same relationship pandapower/PyPSA/Egret/ANDES
each already have with powerio, independently).

User story

As an agent workflow speaking MCP to PowerMCP's tool servers, I want to inspect and edit a
PLEXOS study and translate it toward Sienna — the same way I already call run_power_flow
against pandapower — without a PLEXOS license, installation, or vendor network call.

Why this belongs here

PowerAgent's Model Context Protocol pillar (Zhang & Xie, IEEE PEM 2025) is a tool layer:
multiple engines as peer MCP servers. plexosdb-mcp is purpose-built for exactly this
("agentic integration," "universal interface... without custom API development" per its own
publication) — adopting it is the same compose-don't-rebuild move this repo already makes for
pandapower. PLEXOSDB joins PSS/E, PowerWorld, PSLF, PowerFactory, and PSCAD as a closed-source
engine wrapper, paired (via #54) with a tested, open-source migration path off it.

What will be done

1. One registry entry. Add "plexosdb" (server_dir="PLEXOSDB") to TOOLS in
   powermcp/registry.py. CLI, doctor, the setup wizard, and client-config generation
   already work off this one dict; no other file needs to change to make it discoverable.
2. PLEXOSDB/ connector — thin re-export, same shape as powerio/powerio_mcp.py:
   PLEXOSDB/plexosdb_mcp/main.py re-exports plexosdb_mcp's own FastMCP server object
   (mcp = _server.mcp), covering its ~28 CRUD tools as-is. Adds translate_to_sienna and
   compare_solutions, calling r2x directly at the point of use — no PowerMCP-authored
   bridge module (mirrors how pandapower/PyPSA/Egret/ANDES each import powerio
   directly rather than through a wrapper).
3. Dependency reality check (verified, not assumed):
   • plexosdb-mcp is not on PyPI. Confirmed via uv pip install plexosdb-mcp --dry-run
     (not found) — only the core plexosdb library (v1.5.0) is published. The MCP layer lives
     at NatLabRockies/plexosdb/src/plexosdb-mcp: its own pyproject.toml, v0.1.0, console
     script plexosdb-mcp, deps plexosdb>=1.3.4 + fastmcp>=3.0.0 — a real, cleanly
     packaged project, just not released to PyPI yet.
   • PyPI rejects package metadata that declares a direct git/URL dependency, so
     plexosdb-mcp can't cleanly become a [project.optional-dependencies] entry in
     PowerMCP's own PyPI-published pyproject.toml today (PowerMCP itself ships to PyPI —
     see .github/workflows/publish.yml). Until plexosdb-mcp is on PyPI: document a manual
     two-step install in PLEXOSDB/README.md
     (pip install powermcp, then
     pip install "plexosdb-mcp @ git+https://github.com/NatLabRockies/plexosdb.git@main#subdirectory=src/plexosdb-mcp")
     rather than wiring it into a plexos extra that would break pip install powermcp[plexosdb].
   • The R2X package is r2x (PyPI, v2.1.0 as of this writing — not r2x-cli, which
     does not exist). r2x itself pulls in r2x-core, r2x-plexos, r2x-sienna,
     r2x-plexos-to-sienna, r2x-sienna-to-plexos as its own dependencies; pin r2x alone.
4. License-free tests. PLEXOSDB/tests/test_tools.py mocks translate_to_sienna /
   compare_solutions directly (matching PSCAD/tests/test_tools.py's MagicMock style).
   Extend tests/test_vendor_import.py's pattern to plexosdb_mcp.main, monkeypatching
   plexosdb_mcp to a fake module to assert side-effect-free import — the same
   no-license-required pattern already proven for PSS/E's psspy and PSLF's PSLF_PYTHON.
5. PLEXOSDB/README.md documenting: the manual plexosdb-mcp git install step above, how
   to point the connector at a PLEXOS XML study, and how translate_to_sienna output feeds
   into PowerMCP connector: SIENNA (load/translate-to-PLEXOS/solve via r2x + Julia) #54's SIENNA connector.
6. Proof. A real PLEXOS XML study loads and is inspectable (list objects, memberships,
   properties) through the re-exported tools, and translate_to_sienna produces valid Sienna
   PSY JSON. (Loading that JSON into Sienna and solving is PowerMCP connector: SIENNA (load/translate-to-PLEXOS/solve via r2x + Julia) #54's proof, not this one's.)

Non-goals

• Forking or vendoring plexosdb, plexosdb-mcp, or r2x.
• Requiring a PLEXOS license, install, or vendor network call anywhere in the connector.
• Publishing plexosdb-mcp to PyPI ourselves — that's upstream's call; this issue documents
  the workaround, doesn't route around it permanently.

Acceptance criteria

• powermcp/registry.py has a "plexosdb" entry in TOOLS; pytest tests/test_registry.py
  passes against it unmodified.
• PLEXOSDB/plexosdb_mcp/main.py re-exports plexosdb_mcp's server (mirrors
  powerio/powerio_mcp.py); adds translate_to_sienna, compare_solutions, both calling
  r2x directly.
• r2x (not r2x-cli) pinned in root pyproject.toml's plexosdb extra;
  plexosdb-mcp's git-install documented in PLEXOSDB/README.md, not silently assumed.
• PLEXOSDB/tests/test_tools.py and a plexosdb_mcp.main vendor-import test pass with no
  PLEXOS license or install present.
• One real PLEXOS XML study proven to load → inspect → translate to valid Sienna PSY JSON;
  commands cited in the PR.

References

• plexosdb /
  plexosdb-mcp
  (source only, not yet on PyPI)
• r2x on PyPI, and its
  GitHub repo
• PowerMCP connector: SIENNA (load/translate-to-PLEXOS/solve via r2x + Julia) #54 — the paired SIENNA connector (solve + translate_to_plexos)

[elasticdotventures]

PR #55 opened, ready for review (not draft) — CRUD/inspection is fully proven live.

One known limitation carried into the PR: translate_to_sienna calls the real r2x API correctly, but r2x_plexos==0.2.0 doesn't catch the exception plexosdb now raises (NotFoundError instead of the expected AssertionError) when a model's Horizon has no explicit Chrono Date attributes set — the common case. Reproduces on all 7 models in the real test fixture used, so it isn't fixture-specific. This is an upstream bug, not something fixable in this repo; repro steps are in PLEXOSDB/README.md on the branch. It blocks proving the full PLEXOS→Sienna translation path end-to-end, but doesn't affect the CRUD/inspection tools, which are unaffected and fully verified against a real PLEXOS XML study.

[elasticdotventures]

Follow-up to my earlier comment: the translation blocker is now resolved and verified.

Root cause was two upstream issues stacked on top of each other, not one:

1. r2x_plexos==0.2.0 (pulled in by pinning the r2x meta-package) doesn't catch plexosdb.exceptions.NotFoundError around the Horizon Chrono-attribute lookup — already fixed in r2x_plexos>=0.3.0, confirmed by inspecting the released wheel. Filed NatLabRockies/R2X#299 to get r2x itself to bump its pin.
2. r2x_plexos>=0.3.0 requires plexosdb>=1.6.0, whose plexos2duckdb>=0.1.0b11 dependency has no non-yanked stable release. Filed epri-dev/plexos2duckdb#3.

PR #55 now pins r2x-plexos/r2x-plexos-to-sienna/r2x-sienna directly (bypassing the stale r2x meta-package pin), documents the --prerelease=allow requirement until plexos2duckdb ships a stable release, and re-verifies the full PLEXOS XML → Sienna PSY JSON translation end-to-end against the same real fixture that failed before. All acceptance criteria in this issue are now met.