package tools
import (
"encoding/json"
"fmt"
"strings"
mcpgolang "github.com/metoro-io/mcp-golang"
"github.com/metoro-io/metoro-mcp-server/model"
)
const (
logMessageLengthLimit = 2000
logAttributeValueLengthLimit = 600
stackTraceValueLengthLimit = 300
truncatedValueSuffix = "... [truncated]"
)
var strictLogAttributeKeys = map[string]struct{}{
"errorverbose": {},
"stacktrace": {},
"error": {},
}
var LogsToolResponseGuard = NewToolResponseGuard(trimLargeLogFieldsInToolResponse, ToolResponseGuardOptions{})
func trimLargeLogFieldsInToolResponse(_ string, response *mcpgolang.ToolResponse) (*mcpgolang.ToolResponse, error) {
for _, content := range response.Content {
if content == nil || content.Type != mcpgolang.ContentTypeText || content.TextContent == nil {
continue
}
trimmedText, changed, err := trimLogsPayloadText(content.TextContent.Text)
if err != nil {
return nil, err
}
if changed {
content.TextContent.Text = trimmedText
}
}
return response, nil
}
func trimLogsPayloadText(raw string) (string, bool, error) {
var logsResponse model.GetLogsResponse
if err := json.Unmarshal([]byte(raw), &logsResponse); err != nil {
// Not all tools with this guard necessarily return log payloads all the time.
return raw, false, nil
}
changed := trimLogsModelResponse(&logsResponse)
if !changed {
return raw, false, nil
}
serialized, err := json.Marshal(logsResponse)
if err != nil {
return "", false, fmt.Errorf("failed to marshal trimmed logs response: %w", err)
}
return string(serialized), true, nil
}
func trimLogsModelResponse(logsResponse *model.GetLogsResponse) bool {
changed := false
for i := range logsResponse.Logs {
truncatedMessage, wasTruncated := truncateWithSuffix(logsResponse.Logs[i].Message, logMessageLengthLimit)
if wasTruncated {
logsResponse.Logs[i].Message = truncatedMessage
changed = true
}
if trimLogAttributeValues(logsResponse.Logs[i].LogAttributes) {
changed = true
}
if trimLogAttributeValues(logsResponse.Logs[i].ResourceAttributes) {
changed = true
}
}
return changed
}
func trimLogAttributeValues(attributes map[string]string) bool {
changed := false
for key, value := range attributes {
limit := logAttributeValueLengthLimit
if isStrictlyTrimmedLogAttribute(key) {
limit = stackTraceValueLengthLimit
}
trimmed, wasTruncated := truncateWithSuffix(value, limit)
if wasTruncated {
attributes[key] = trimmed
changed = true
}
}
return changed
}
func isStrictlyTrimmedLogAttribute(attributeKey string) bool {
key := strings.ToLower(strings.TrimSpace(attributeKey))
_, ok := strictLogAttributeKeys[key]
return ok
}
func truncateWithSuffix(value string, limit int) (string, bool) {
runes := []rune(value)
if limit <= 0 || len(runes) <= limit {
return value, false
}
suffixRunes := []rune(truncatedValueSuffix)
if limit <= len(suffixRunes) {
return string(suffixRunes[:limit]), true
}
return string(runes[:limit-len(suffixRunes)]) + truncatedValueSuffix, true
}
