MCP Materials Server

Instructions

Implementation Reference

• src/mcp_materials/server.py:327-396 (handler)

  The handler function for the 'search_by_band_gap' MCP tool. Decorated with @mcp.tool(), it queries the Materials Project database for materials within a specified band gap range (min_gap to max_gap), optionally filtering for direct band gaps only. Returns JSON with matching materials including material_id, formula, band_gap, stability, etc.
  @mcp.tool() def search_by_band_gap( min_gap: float = 0.0, max_gap: float = 10.0, direct_gap_only: bool = False, max_results: int = 10, ) -> str: """ Search for materials by band gap range. Args: min_gap: Minimum band gap in eV (default: 0) max_gap: Maximum band gap in eV (default: 10) direct_gap_only: Only return materials with direct band gaps max_results: Maximum number of results (default: 10) Returns: JSON with materials in the specified band gap range """ has_key, key_or_error = check_api_key() if not has_key: return json.dumps({"error": key_or_error}) try: from mp_api.client import MPRester with MPRester(key_or_error) as mpr: search_kwargs: dict[str, Any] = { "band_gap": (min_gap, max_gap), "fields": [ "material_id", "formula_pretty", "band_gap", "is_gap_direct", "energy_above_hull", "is_stable", ], "num_chunks": 1, "chunk_size": max_results * 2, # Get extra in case we filter } if direct_gap_only: search_kwargs["is_gap_direct"] = True docs = mpr.materials.summary.search(**search_kwargs) results = [] for doc in docs: if len(results) >= max_results: break results.append({ "material_id": str(doc.material_id), "formula": doc.formula_pretty, "band_gap_eV": doc.band_gap, "is_direct_gap": doc.is_gap_direct, "energy_above_hull_eV": doc.energy_above_hull, "is_stable": doc.is_stable, }) return json.dumps({ "query": { "band_gap_range_eV": [min_gap, max_gap], "direct_gap_only": direct_gap_only, }, "count": len(results), "materials": results, }, indent=2) except Exception as e: return json.dumps({"error": str(e)})