alibaba/open-code-review · error

tool names in %s must not be empty

Error message

tool names in %s must not be empty

What it means

After successfully parsing the tools JSON array, setMCPServerValue rejects empty strings inside the array with "tool names in <server> must not be empty". Empty tool names would never match a server-exposed tool, so they are treated as config mistakes.

Source

Thrown at cmd/opencodereview/config_cmd.go:915

			return fmt.Errorf("MCP server URL %q must include a host", value)
		}
		entry.URL = value
	case "headers":
		parsed, err := parseMCPHeaders(value)
		if err != nil {
			return fmt.Errorf("invalid headers for %s: %w", key, err)
		}
		entry.Headers = parsed
	case "tools":
		var tools []string
		if err := json.Unmarshal([]byte(value), &tools); err != nil {
			return fmt.Errorf("invalid JSON array for %s: %w", key, err)
		}
		seen := make(map[string]struct{}, len(tools))
		filtered := make([]string, 0, len(tools))
		for _, t := range tools {
			if t == "" {
				return fmt.Errorf("tool names in %s must not be empty", key)
			}
			if _, dup := seen[t]; dup {
				continue
			}
			seen[t] = struct{}{}
			filtered = append(filtered, t)
		}
		entry.Tools = filtered
	case "setup":
		entry.Setup = value
	default:
		return fmt.Errorf("unknown MCP server field %q: supported fields are type, command, args, env, url, headers, tools, setup", field)
	}

	cfg.MCPServers[name] = entry
	return nil
}

View on GitHub (pinned to 5cf97d0d15)

Solutions

1. Remove the empty entry: `ocr config set mcp-servers.myserver.tools '["read_file"]'`
2. Check for double or trailing commas in the array
3. Verify each tool name against the server's advertised tool list

Example fix

// before
ocr config set mcp-servers.myserver.tools '["read_file",]'
// after
ocr config set mcp-servers.myserver.tools '["read_file"]'

func hasNoEmptyNames(s string) bool {
    var a []string
    if json.Unmarshal([]byte(s), &a) != nil { return false }
    for _, t := range a { if t == "" { return false } }
    return len(a) > 0
}

func allNonEmpty(xs []string) bool { for _, x := range xs { if x == "" { return false } }; return true }

if err := setMCPServerValue(cfg, name, "tools", raw); err != nil {
    if strings.Contains(err.Error(), "must not be empty") { /* drop empty entries and retry */ }
    return err
}

When it happens

Trigger: A tools array containing "" — e.g. '["read_file",""]' — usually from a trailing comma in a hand-written list, or from splitting an empty string into an element.

Common situations: Trailing comma left inside the JSON array; programmatic construction joining values with commas producing "a,,b"; placeholder left unfilled.

Related errors

• MCP server %q not found
• invalid max_tokens %q: must be a positive integer
• unknown config key: %s Supported keys: %s Provider fields: a
• invalid URL for %s: %w
• invalid model list for %s: %w

AI-assisted analysis of alibaba/open-code-review@5cf97d0d15 (2026-09-02). Data as JSON: /api/errors/db9769bccc50676d. Report an issue: GitHub.