USolver

Instructions

Implementation Reference

• usolver_mcp/solvers/cvxpy_solver.py:55-110 (handler)

  Core handler function that implements the CVXPY problem solving logic: creates variables, parses expressions for objective and constraints, solves the problem, extracts values and duals.
  def solve_cvxpy_problem(problem: CVXPYProblem) -> Result[CVXPYSolution, str]: """Solve a CVXPY optimization problem. Args: problem: The problem definition Returns: Result containing a CVXPYSolution or an error message """ try: # Create variables variables: dict[str, cp.Variable] = {} for var in problem.variables: variables[var.name] = create_variable(var.name, var.shape) # Parse objective objective_expr = parse_expression( problem.objective.expression, variables, problem.parameters ) objective = ( cp.Minimize(objective_expr) if problem.objective.type == ObjectiveType.MINIMIZE else cp.Maximize(objective_expr) ) # Parse constraints constraints = [] for _i, constraint in enumerate(problem.constraints): constraint_expr = parse_expression( constraint.expression, variables, problem.parameters ) constraints.append(constraint_expr) # Create and solve the problem prob = cp.Problem(objective, constraints) result = prob.solve() # Extract solution values = {name: var.value for name, var in variables.items()} dual_values = { i: constraint.dual_value for i, constraint in enumerate(constraints) if hasattr(constraint, "dual_value") and constraint.dual_value is not None } return Success( CVXPYSolution( values=values, objective_value=float(result) if result is not None else None, status=prob.status, dual_values=dual_values if dual_values else None, ) ) except Exception as e: return Failure(f"Error solving CVXPY problem: {e!s}")
• usolver_mcp/server/main.py:398-462 (handler)

  MCP tool handler registered with @app.tool('solve_cvxpy_problem'). Calls the core solve_cvxpy_problem function and formats the result as TextContent for MCP response.
  @app.tool("solve_cvxpy_problem") async def solve_cvxpy_problem_tool(problem: CVXPYProblem) -> list[TextContent]: """Solve a CVXPY optimization problem. This tool takes a CVXPY optimization problem defined with variables, objective, and constraints, and returns a solution if one exists. Example: Solve the following problem: minimize ||Ax - b||₂² subject to: 0 ≤ x ≤ 1 where A = [1.0, -0.5; 0.5, 2.0; 0.0, 1.0] and b = [2.0, 1.0, -1.0] Should be this tool call: simple_cvxpy_solver( variables=[{"name": "x", "shape": 2}], objective_type="minimize", objective_expr="cp.sum_squares(np.array(A) @ x - np.array(b))", constraints=["x >= 0", "x <= 1"], parameters={"A": [[1.0, -0.5], [0.5, 2.0], [0.0, 1.0]], "b": [2.0, 1.0, -1.0]} ) Args: problem: The problem definition with variables, objective, and constraints Returns: A list of TextContent containing the solution or an error message """ result = solve_cvxpy_problem(problem) match result: case Success(solution): return [ TextContent( type="text", text=json.dumps( { "values": { k: v.tolist() if hasattr(v, "tolist") else v for k, v in solution.values.items() }, "objective_value": solution.objective_value, "status": solution.status, "dual_values": { k: v.tolist() if hasattr(v, "tolist") else v for k, v in (solution.dual_values or {}).items() }, } ), ) ] case Failure(error): return [TextContent(type="text", text=f"Error solving problem: {error}")] case _: return [ TextContent( type="text", text="Unexpected error in solve_cvxpy_problem_tool", ) ]
• usolver_mcp/server/main.py:398-398 (registration)

  Registration of the 'solve_cvxpy_problem' tool using FastMCP's @app.tool decorator.
  @app.tool("solve_cvxpy_problem")
• usolver_mcp/models/cvxpy_models.py:1-52 (schema)

  Pydantic models defining the input schema (CVXPYProblem, CVXPYVariable, etc.) and output (CVXPYSolution) for the CVXPY solver.
  from enum import Enum from typing import Any from pydantic import BaseModel class ObjectiveType(str, Enum): """Enum for objective types in CVXPY.""" MINIMIZE = "minimize" MAXIMIZE = "maximize" class CVXPYVariable(BaseModel): """Model representing a CVXPY variable.""" name: str shape: int | tuple[int, ...] # Can be scalar (int) or vector/matrix (tuple) class CVXPYConstraint(BaseModel): """Model representing a CVXPY constraint.""" expression: str # String representation of the constraint description: str = "" class CVXPYObjective(BaseModel): """Model representing a CVXPY objective.""" type: ObjectiveType expression: str # String representation of the objective function class CVXPYProblem(BaseModel): """Model representing a complete CVXPY optimization problem.""" variables: list[CVXPYVariable] objective: CVXPYObjective constraints: list[CVXPYConstraint] parameters: dict[str, Any] = {} # For A, b, etc. description: str = "" class CVXPYSolution(BaseModel): """Model representing a solution to a CVXPY problem.""" values: dict[str, Any] # Variable values objective_value: float | None status: str dual_values: dict[int, Any] | None = None # Constraint index to dual value
• usolver_mcp/solvers/cvxpy_solver.py:30-52 (helper)

  Helper function to parse string expressions into CVXPY expressions using safe eval with variables and parameters.
  def parse_expression( expr_str: str, variables: dict[str, cp.Variable], params: dict[str, Any] ) -> CVXPYExpr: """Parse a CVXPY expression string. Args: expr_str: String representation of the expression variables: Dictionary of variable names to CVXPY variables params: Dictionary of parameter names to values Returns: Parsed CVXPY expression """ # Create a local dictionary with variables and parameters local_dict = { **variables, **params, "cp": cp, "np": np, } # Evaluate the expression in the context of the local dictionary return eval(expr_str, {"__builtins__": {}}, local_dict)