Function transformMCPResult

src/node/services/mcpResultTransform.ts:64–130

(result: unknown)

 * Truncates large images to prevent context overflow.
 */
export function transformMCPResult(result: unknown): unknown {
  if (!result || typeof result !== "object") {
    return result;
  }

  const typed = result as MCPCallToolResult;

  // If it's an error or has toolResult, pass through as-is
  if (typed.isError || typed.toolResult !== undefined) {
    return result;
  }

  // If no content array, pass through
  if (!typed.content || !Array.isArray(typed.content)) {
    return result;
  }

  // Check if any content is an image
  const hasImage = typed.content.some((c) => c.type === "image");
  if (!hasImage) {
    return result;
  }

  // Debug: log what we received from MCP
  log.debug("[MCP] transformMCPResult input", {
    contentTypes: typed.content.map((c) => c.type),
    imageItems: typed.content
      .filter((c): c is MCPImageContent => c.type === "image")
      .map((c) => ({ type: c.type, mimeType: c.mimeType, dataLen: c.data?.length })),
  });

  // Transform to AI SDK content format
  const transformedContent: AISDKContentPart[] = typed.content.map((item) => {
    if (item.type === "text") {
      return { type: "text" as const, text: item.text };
    }
    if (item.type === "image") {
      const imageItem = item;
      // Check if image data exceeds the limit
      const dataLength = imageItem.data?.length ?? 0;
      if (dataLength > MAX_IMAGE_DATA_BYTES) {
        log.warn("[MCP] Image data too large, omitting from context", {
          mimeType: imageItem.mimeType,
          dataLength,
          maxAllowed: MAX_IMAGE_DATA_BYTES,
        });
        return {
          type: "text" as const,
          text: `[Image omitted: ${formatBytesSI(dataLength)} exceeds per-image guard of ${formatBytesSI(MAX_IMAGE_DATA_BYTES)}. Reduce resolution or quality and retry.]`,
        };
      }
      // Ensure mediaType is present - default to image/png if missing
      const mediaType = imageItem.mimeType || "image/png";
      log.debug("[MCP] Transforming image content", { mimeType: imageItem.mimeType, mediaType });
      return { type: "media" as const, data: imageItem.data, mediaType };
    }
    // For resource type, convert to text representation
    if (item.type === "resource") {