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fix: disable Unicode escaping in JSON output and correct Meta type assignment #526

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fix: disable Unicode escaping in JSON output and correct Meta type assignment #526

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c501bc3
fix: disable Unicode escaping in JSON output
longkeyy Aug 3, 2025
1951206
fix: correct Meta type assignment in CallToolResult unmarshaling
longkeyy Aug 3, 2025
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4 changes: 3 additions & 1 deletion mcp/tools.go
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Original file line number Diff line number Diff line change
Expand Up @@ -504,7 +504,9 @@ func (r *CallToolResult) UnmarshalJSON(data []byte) error {
// Unmarshal Meta
if meta, ok := raw["_meta"]; ok {
if metaMap, ok := meta.(map[string]any); ok {
r.Meta = metaMap
r.Meta = &Meta{
AdditionalFields: metaMap,
}
}
}

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12 changes: 10 additions & 2 deletions server/stdio.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package server

import (
"bufio"
"bytes"
"context"
"encoding/json"
"fmt"
Expand Down Expand Up @@ -457,11 +458,18 @@ func (s *StdioServer) writeResponse(
response mcp.JSONRPCMessage,
writer io.Writer,
) error {
responseBytes, err := json.Marshal(response)
if err != nil {
// Create a buffer to write JSON with custom encoding settings
var buf bytes.Buffer
encoder := json.NewEncoder(&buf)
encoder.SetEscapeHTML(false) // Disable HTML escaping, which also prevents Unicode escaping

if err := encoder.Encode(response); err != nil {
return err
}

// Remove the trailing newline added by Encode() and add our own
responseBytes := bytes.TrimSuffix(buf.Bytes(), []byte("\n"))

// Write response followed by newline
if _, err := fmt.Fprintf(writer, "%s\n", responseBytes); err != nil {
return err
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