Desmos MCP Server

Instructions

Implementation Reference

• src/main.py:102-172 (handler)

  The main handler function for the 'plot_math_function' tool. It handles plotting using Desmos API if available, falling back to local SymPy rendering, and returns a base64-encoded image URI.

  @mcp.tool()
  async def plot_math_function(
      ctx: MCPContext,
      formula: str,
      x_range: Optional[List[float]] = [-10, 10],
      y_range: Optional[List[float]] = None,
      use_api: bool = True
  ) -> str:
      """Generates a 2D plot. Tries Desmos API if available, otherwise falls back to local rendering."""
      await ctx.progress.start(message="Initializing plot...")
      
      if use_api and desmos_client:
          ctx.info("Attempting to plot with Desmos API...")
          await ctx.progress.report(1, 2, "Calling Desmos API...")
          try:
              image_bytes = await desmos_client.plot_formula(formula, x_range, y_range)
              if image_bytes:
                  await ctx.progress.report(2, 2, "Encoding image...")
                  img_base64 = base64.b64encode(image_bytes).decode('utf-8')
                  data_uri = f"data:image/png;base64,{img_base64}"
                  await ctx.progress.end()
                  return f"Successfully plotted '{formula}' using Desmos API. Image: {data_uri}"
              else:
                  ctx.warning("Desmos API call failed, falling back to local rendering.")
          except Exception as e:
              ctx.error(f"An exception occurred with Desmos API: {e}. Falling back to local rendering.")
  
      ctx.info("Using local rendering...")
      try:
          await ctx.progress.start(total=3, message="Starting local rendering...")
          
          await ctx.progress.report(1, 3, "Parsing formula...")
          expr = sympy.sympify(formula)
          x = sympy.symbols('x')
  
          await ctx.progress.report(2, 3, "Generating plot data...")
          plot_kwargs = {
              'show': False,
              'xlabel': 'x',
              'ylabel': 'y',
              'title': formula
          }
          if x_range:
              plot_kwargs['xlim'] = x_range
          if y_range:
              plot_kwargs['ylim'] = y_range
  
          p = sympy.plot(expr, (x, x_range[0], x_range[1]), **plot_kwargs)
  
          # Save the plot to a file
          desktop_path = os.path.join(os.path.expanduser('~'), 'Desktop')
          save_dir = os.path.join(desktop_path, 'Desmos-MCP')
          os.makedirs(save_dir, exist_ok=True)
          timestamp = datetime.now().strftime("%Y%m%d%H%M%S")
          filename = f"plot_{timestamp}.png"
          p.save(os.path.join(save_dir, filename))
  
          await ctx.progress.report(3, 3, "Encoding image...")
          buf = io.BytesIO()
          p.save(buf)
          buf.seek(0)
          img_base64 = base64.b64encode(buf.read()).decode('utf-8')
          data_uri = f"data:image/png;base64,{img_base64}"
          
          await ctx.progress.end()
          return f"Successfully plotted '{formula}' using local rendering. Image: {data_uri}"
  
      except Exception as e:
          await ctx.progress.end()
          return f"Error plotting formula '{formula}' locally. Details: {e}"

• src/desmos_api.py:17-41 (helper)

  Supporting method in DesmosAPIClient that performs the actual API call to plot the formula, used by the main handler when use_api is True.

  async def plot_formula(self, formula: str, x_range: List[float], y_range: List[float]) -> Optional[bytes]:
      """Requests a plot from the Desmos API and returns the image bytes."""
      headers = {
          "Authorization": f"Bearer {self.api_key}"
      }
      # 注意：此处的 payload 结构是基于通用 API 设计的推断，可能需要根据实际的 Desmos API 文档进行调整
      payload = {
          "formula": formula,
          "x_range": x_range,
          "y_range": y_range,
          "format": "png"
      }
      
      async with httpx.AsyncClient() as client:
          try:
              response = await client.post(f"{API_BASE_URL}/plot", headers=headers, json=payload, timeout=15.0)
              response.raise_for_status() # 如果状态码是 4xx 或 5xx，则引发异常
              return response.content
          except httpx.HTTPStatusError as e:
              print(f"Desmos API returned an error: {e.response.status_code} {e.response.text}")
              return None
          except httpx.RequestError as e:
              print(f"Error connecting to Desmos API: {e}")
              return None