Conciseness

The body is dense with executable code and domain-critical caveats ('A registered GPU plugin does not prove a working device or driver', unit-conversion warnings) rather than padding, but has minor trimmable content: the one-sentence definition of molecular dynamics, repeated import blocks across sections, and some docstring verbosity. It is efficient but not the fully lean anchor 5 where every token earns its place.

Actionability

Complete, copy-paste-ready Python functions cover system preparation, minimization, NVT, NPT/production, trajectory loading, RMSD, RMSF, contacts, and plotting, with pinned install commands ('uv pip install --python .venv-md/bin/python "openmm==8.6.1"...'), explicit parameters, and precondition error handling. This matches the fully-executable anchor 5.

Workflow Clarity

The sequence is clearly staged and numbered (System Preparation → Energy Minimization → NVT → NPT/Production, then analysis steps 1-4) with explicit validation checkpoints: initial/minimized energy prints, ValueError raises for invalid preconditions ('NVT requires all barostats disabled', 'NPT requires a periodic system'), and 'Inspect density, energy, structure and replicate stability before a separate production call'. It falls short of anchor 5 only because explicit error-recovery feedback loops (validate → fix → retry) are not spelled out.

Progressive Disclosure

The SKILL.md keeps the core workflow inline and moves advanced material to two real, well-signaled, one-level-deep references — 'See [analysis reference](references/mdanalysis_analysis.md) for alignment, PCA, DSSP, hydrogen bonds and population-derived free energy' and 'See [preparation reference](references/system_preparation.md) for conservative PDBFixer and OpenFF examples' — both verified to exist with content matching their descriptions. This matches the clear-overview anchor 5 with no buried or nested references.

Specificity

The description lists multiple concrete actions — 'Runs and analyzes molecular dynamics simulations', 'Sets up protein/small molecule systems, defines force fields, runs energy minimization and production MD, and analyzes trajectories (RMSD, RMSF, contact maps, free energy surfaces)' — with comprehensive, tool-specific coverage. It exceeds anchor 4 ('several specific actions; minor gaps') because the action list spans setup, simulation, and analysis with named observables.

Completeness

The 'what' is explicit and concrete (runs/sets up/analyzes MD with named tools and observables), and a 'when' is present via 'For structural biology, drug binding, and biophysics.' It is not anchor 3 because the 'when' is explicitly stated rather than missing or merely implied, but not anchor 5 because that clause is domain scoping rather than concrete task-level trigger phrases ('Use when the user asks to run MD simulations, compute RMSD...').

Trigger Term Quality

Good natural keyword coverage: 'molecular dynamics', 'simulations', 'protein', 'trajectories', 'RMSD', 'RMSF', 'free energy', 'drug binding', 'OpenMM', 'MDAnalysis'. A few natural terms users would say are missing (e.g., 'MD simulation' variants, trajectory file extensions like .dcd/.xtc), so it falls between anchor 4 and 5 but is not the comprehensive synonym/extension coverage of anchor 5.

Distinctiveness Conflict Risk

Named engines (OpenMM, MDAnalysis) plus specific observables (RMSD, RMSF, contact maps, free energy surfaces) carve a clear niche with minimal conflict risk; a user mentioning these terms almost certainly needs this exact skill. It matches anchor 5 and is more distinct than anchor 4's 'minor overlap risk with closely related skills'.