MCP Materials Server

Instructions

Get the crystal structure for a material from Materials Project.

Args:
    material_id: Materials Project ID (e.g., "mp-149" for Silicon)
    format: Output format - "cif", "poscar", or "json" (default: "cif")

Returns:
    Crystal structure in the requested format

Implementation Reference

• src/mcp_materials/server.py:109-149 (handler)

  The main handler function for the 'get_structure' tool, decorated with @mcp.tool() for automatic registration and schema generation from type hints and docstring. Fetches crystal structure data from Materials Project API and returns in CIF, POSCAR, or JSON format.

  @mcp.tool()
  def get_structure(
      material_id: str,
      format: str = "cif",
  ) -> str:
      """
      Get the crystal structure for a material from Materials Project.
  
      Args:
          material_id: Materials Project ID (e.g., "mp-149" for Silicon)
          format: Output format - "cif", "poscar", or "json" (default: "cif")
  
      Returns:
          Crystal structure in the requested format
      """
      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:
              structure = mpr.get_structure_by_material_id(material_id)
  
              if format.lower() == "cif":
                  from pymatgen.io.cif import CifWriter
                  return CifWriter(structure).__str__()
              elif format.lower() == "poscar":
                  from pymatgen.io.vasp import Poscar
                  return Poscar(structure).get_str()
              elif format.lower() == "json":
                  return structure.to_json()
              else:
                  return json.dumps({"error": f"Unknown format: {format}. Use 'cif', 'poscar', or 'json'"})
  
      except ImportError:
          return json.dumps({"error": "mp-api or pymatgen not installed"})
      except Exception as e:
          return json.dumps({"error": str(e)})

• src/mcp_materials/server.py:109-109 (registration)

  The @mcp.tool() decorator registers the get_structure function as an MCP tool.

  @mcp.tool()

• src/mcp_materials/server.py:110-123 (schema)

  Input schema defined by function parameters (material_id: str, format: str = 'cif') and comprehensive docstring describing args and return value. Output is str (structure file content or JSON error).

  def get_structure(
      material_id: str,
      format: str = "cif",
  ) -> str:
      """
      Get the crystal structure for a material from Materials Project.
  
      Args:
          material_id: Materials Project ID (e.g., "mp-149" for Silicon)
          format: Output format - "cif", "poscar", or "json" (default: "cif")
  
      Returns:
          Crystal structure in the requested format
      """