Function convertCallResult

coderd/x/chatd/mcpclient/mcpclient.go:671–811

convertCallResult translates an MCP CallToolResult into a fantasy.ToolResponse. The fantasy response model supports a single content type per response, so we prioritize text. All text items are collected first. Binary items (image, audio, or embedded blob) are only returned when no text content is a

(
	result *mcp.CallToolResult,
)

// or embedded blob) are only returned when no text content is
// available.
func convertCallResult(
	result *mcp.CallToolResult,
) fantasy.ToolResponse {
	if result == nil {
		return fantasy.NewTextResponse("")
	}

	var (
		textParts    []string
		binaryResult *fantasy.ToolResponse
	)
	for _, item := range result.Content {
		switch c := item.(type) {
		case mcp.TextContent:
			textParts = append(textParts, strings.ToValidUTF8(c.Text, "\uFFFD"))
		case mcp.ImageContent:
			data, err := base64.StdEncoding.DecodeString(
				c.Data,
			)
			if err != nil {
				textParts = append(textParts,
					"[image decode error: "+err.Error()+"]",
				)
				continue
			}
			if binaryResult == nil {
				r := fantasy.ToolResponse{
					Type:      "image",
					Data:      data,
					MediaType: c.MIMEType,
					IsError:   result.IsError,
				}
				binaryResult = &r
			}
		case mcp.AudioContent:
			data, err := base64.StdEncoding.DecodeString(
				c.Data,
			)
			if err != nil {
				textParts = append(textParts,
					"[audio decode error: "+err.Error()+"]",
				)
				continue
			}
			if binaryResult == nil {
				r := fantasy.ToolResponse{
					Type:      "media",
					Data:      data,
					MediaType: c.MIMEType,
					IsError:   result.IsError,
				}
				binaryResult = &r
			}
		case mcp.EmbeddedResource:
			// Embedded resources wrap either text or blob
			// content from an MCP resource. We handle each
			// variant so the LLM receives the content
			// regardless of form.