googleapis/mcp-toolbox · error

tool type %q already registered

Error message

tool type %q already registered

What it means

The package's init() registers the 'postgres-list-tables' tool type in the global registry and panics if tools.Register returns false, meaning the type string was already claimed. This is a duplicate-registration guard for programming errors (e.g. a vendored or duplicated package copy linked into the binary), not a user config issue.

Source

Thrown at internal/tools/postgres/postgreslisttables/postgreslisttables.go:112

                'object_type', CASE ti.object_kind
                                WHEN 'r' THEN 'TABLE'
                                WHEN 'p' THEN 'PARTITIONED TABLE'
                                ELSE ti.object_kind::text -- Should not happen due to WHERE clause
                            END,
                'owner', ti.table_owner,
                'comment', ti.table_comment,
                'columns', COALESCE((SELECT json_agg(json_build_object('column_name',ci.column_name,'data_type',ci.data_type,'ordinal_position',ci.column_ordinal_position,'is_not_nullable',ci.is_not_nullable,'column_default',ci.column_default,'column_comment',ci.column_comment) ORDER BY ci.column_ordinal_position) FROM columns_info ci WHERE ci.table_oid = ti.table_oid), '[]'::json),
                'constraints', COALESCE((SELECT json_agg(json_build_object('constraint_name',cons.constraint_name,'constraint_type',cons.constraint_type,'constraint_definition',cons.constraint_definition,'constraint_columns',cons.constraint_columns,'foreign_key_referenced_table',cons.foreign_key_referenced_table,'foreign_key_referenced_columns',cons.foreign_key_referenced_columns)) FROM constraints_info cons WHERE cons.table_oid = ti.table_oid), '[]'::json),
                'indexes', COALESCE((SELECT json_agg(json_build_object('index_name',ii.index_name,'index_definition',ii.index_definition,'is_unique',ii.is_unique,'is_primary',ii.is_primary,'index_method',ii.index_method,'index_columns',ii.index_columns)) FROM indexes_info ii WHERE ii.table_oid = ti.table_oid), '[]'::json),
                'triggers', COALESCE((SELECT json_agg(json_build_object('trigger_name',tri.trigger_name,'trigger_definition',tri.trigger_definition,'trigger_enabled_state',tri.trigger_enabled_state)) FROM triggers_info tri WHERE tri.table_oid = ti.table_oid), '[]'::json)
            )
        END AS object_details
    FROM table_info ti ORDER BY ti.schema_name, ti.table_name;
`

func init() {
	if !tools.Register(resourceType, newConfig) {
		panic(fmt.Sprintf("tool type %q already registered", resourceType))
	}
}

func newConfig(ctx context.Context, name string, decoder *yaml.Decoder) (tools.ToolConfig, error) {
	actual := Config{ConfigBase: tools.ConfigBase{Name: name}}
	if err := decoder.DecodeContext(ctx, &actual); err != nil {
		return nil, err
	}
	return actual, nil
}

type compatibleSource interface {
	PostgresPool() *pgxpool.Pool
	RunSQL(context.Context, string, []any) (any, error)
}

type Config struct {
	tools.ConfigBase `yaml:",inline"`

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Ensure the package is not imported twice under different paths (e.g. vendored and module copies)
2. Rename the conflicting resourceType constant if two distinct tools share it
3. Clean go.mod/go.sum and rebuild to eliminate stale duplicate dependencies

When it happens

Trigger: Thrown at internal/tools/postgres/postgreslisttables/postgreslisttables.go:112 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/ec3860f98c6c46a8. Report an issue: GitHub.