googleapis/mcp-toolbox · error

can't convert %s to array of strings: %w

Error message

can't convert %s to array of strings: %w

What it means

InvokeSearchCatalog converts the optional parent parameter (parentParamName, e.g. a location/collection parent resource list) from []any to []string. Non-string elements or an absent value fail the conversion and produce this formatted error naming the parameter. It enforces the tool's declared parameter types at runtime.

Source

Thrown at internal/sources/dataplex/searchcatalog/search_catalog.go:152

	tokenStr string,
	systemName string,
	parentParamName string,
	typeMap map[string]string,
	projectID string,
	getCatalogClient func(ctx context.Context, token string) (*dataplexapi.CatalogClient, error),
) ([]DataplexSearchResponse, error) {
	pageSize := int32(paramsMap["pageSize"].(int))
	prompt, _ := paramsMap["prompt"].(string)

	projectIdSlice, err := parameters.ConvertAnySliceToTyped(paramsMap["projectIds"].([]any), "string")
	if err != nil {
		return nil, fmt.Errorf("can't convert projectIds to array of strings: %w", err)
	}
	projectIds := projectIdSlice.([]string)

	parentIdSlice, err := parameters.ConvertAnySliceToTyped(paramsMap[parentParamName].([]any), "string")
	if err != nil {
		return nil, fmt.Errorf("can't convert %s to array of strings: %w", parentParamName, err)
	}
	parentIds := parentIdSlice.([]string)

	typesSlice, err := parameters.ConvertAnySliceToTyped(paramsMap["types"].([]any), "string")
	if err != nil {
		return nil, fmt.Errorf("can't convert types to array of strings: %w", err)
	}
	types := typesSlice.([]string)

	query := ConstructSearchQuery(prompt, projectIds, parentIds, types, systemName)

	req := &dataplexpb.SearchEntriesRequest{
		Query:          query,
		Name:           fmt.Sprintf("projects/%s/locations/global", projectID),
		PageSize:       pageSize,
		SemanticSearch: true,
	}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Provide the parent param as a JSON array of strings, or omit it entirely only if the tool schema permits
2. Convert null to [] before sending
3. Check the tool manifest to confirm the exact parentParamName and its type
4. Add client-side validation that all list elements are strings

Example fix

// before
{"parent": null}
// after
{"parent": ["projects/my-project/locations/us-central1"]}

if v, present := paramsMap[parentParamName]; present && v == nil { delete(paramsMap, parentParamName) }
// or coerce: if v == nil { paramsMap[parentParamName] = []any{} }

parents, ok := paramsMap[parentParamName].([]any); if ok && !allStrings(parents) { ... }

res, err := searchcatalog.InvokeSearchCatalog(ctx, src, params)
if err != nil {
	if strings.Contains(err.Error(), fmt.Sprintf("can't convert %s", parentParamName)) {
		return fmt.Errorf("%s must be an array of strings", parentParamName)
	}
	return err
}

When it happens

Trigger: Invoking search_catalog with the parent parameter containing non-string values or being nil when unmarshaled (null instead of an array).

Common situations: Agents sending null for optional list params; mixing numeric enum values into the parent list; schema drift between the client tool manifest and the server's expected types.

Related errors

• can't convert projectIds to array of strings: %w
• can't convert types to array of strings: %w
• dataplex catalog client is nil
• failed to create search entries iterator
• can't convert fields to array of strings: %s

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/2448a61d2efb2b16. Report an issue: GitHub.