googleapis/mcp-toolbox · error

invalid protocol: %s, must be one of: http, https

Error message

invalid protocol: %s, must be one of: http, https

What it means

validateConfig rejects a ClickHouse source config whose protocol field is neither empty, 'http', nor 'https'. The protocol selects the DSN scheme used to build the clickhouse-go connection string, so only these two values are meaningful.

Source

Thrown at internal/sources/clickhouse/clickhouse.go:175

			default:
				vMap[name] = rawValues[i]
			}
		}
		out = append(out, vMap)
	}

	if err := results.Err(); err != nil {
		return nil, fmt.Errorf("errors encountered by results.Scan: %w", err)
	}

	return out, nil
}

func validateConfig(protocol string) error {
	validProtocols := map[string]bool{"http": true, "https": true}

	if protocol != "" && !validProtocols[protocol] {
		return fmt.Errorf("invalid protocol: %s, must be one of: http, https", protocol)
	}
	return nil
}

func initClickHouseConnectionPool(ctx context.Context, tracer trace.Tracer, name, host, port, user, pass, dbname, protocol string, secure bool) (*sql.DB, error) {
	//nolint:all // Reassigned ctx
	ctx, span := sources.InitConnectionSpan(ctx, tracer, SourceType, name)
	defer span.End()

	if protocol == "" {
		protocol = "https"
	}

	if err := validateConfig(protocol); err != nil {
		return nil, err
	}

	encodedUser := url.QueryEscape(user)

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Change protocol in the source YAML to 'http' or 'https' (lowercase)
2. Remove the protocol field entirely — an empty value is accepted and treated as non-secure default
3. Check for stray whitespace or capitalization in the YAML value

Example fix

// before
protocol: "tcp"
// after
protocol: "https"

func validProtocol(p string) bool { return p == "" || p == "http" || p == "https" }
// call before writing config: if !validProtocol(cfg.Protocol) { return errors.New("protocol must be http or https") }

When it happens

Trigger: Setting protocol to any non-empty string other than 'http' or 'https' in the source YAML (e.g. 'tcp', 'HTTP', 'native') when declaring the clickhouse source; Initialize then calls validateConfig before opening the pool.

Common situations: Copy-pasting a native clickhouse-client port config (protocol 'tcp') from another tool, or using uppercase/lowercase typos like 'HTTPS' when wiring the YAML config.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• `introspectionEndpoint` is not allowed when `mcpEnabled` is
• `introspectionMethod` is not allowed when `mcpEnabled` is fa
• `introspectionParamName` is not allowed when `mcpEnabled` is
• error parsing argument: %w
• invalid role %q: must be 'user' or 'assistant'

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/ba9cd263ff28f509. Report an issue: GitHub.