googleapis/mcp-toolbox · error · Error

Invalid number "${item}" found in array for ${paramName} at

Error message

Invalid number "${item}" found in array for ${paramName} at index ${index}.

What it means

A "referenceValue" must carry a string payload (the document path). If the value under "referenceValue" is any other JSON type, this error is returned. Valid string references are converted to a *firestore.DocumentRef when a client is provided, otherwise returned as the path string.

Source

Thrown at internal/server/static/js/runTool.js:146

function parseArrayParameter(rawValue, valueType, paramName) {
    const ELEMENT_TYPE = valueType.substring(6, valueType.length - 1);
    let parsedArray;
    try {
        parsedArray = JSON.parse(rawValue);
    } catch (e) {
        throw new Error(`Invalid JSON format for ${paramName}. Expected an array. ${e.message}`);
    }

    if (!Array.isArray(parsedArray)) {
        throw new Error(`Input for ${paramName} must be a JSON array (e.g., ["a", "b"]).`);
    }

    return parsedArray.map((item, index) => {
        switch (ELEMENT_TYPE) {
            case 'number':
                const NUM = Number(item);
                if (isNaN(NUM)) {
                    throw new Error(`Invalid number "${item}" found in array for ${paramName} at index ${index}.`);
                }
                return NUM;
            case 'boolean':
                return item === true || String(item).toLowerCase() === 'true';
            case 'string':
            default:
                return item;
        }
    });
}

/**
 * Displays the results from the tool run in the response area.
 */
export function displayResults(results, responseArea, prettify) {
    if (results === null || results === undefined) {
        return;
    }

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Provide the reference as a plain document path string, e.g. "projects/p/databases/(default)/documents/users/u1" or "users/u1".
2. Pass a non-nil firestore client if you want automatic conversion to a *firestore.DocumentRef.
3. Omit the field entirely if the reference is unset.

Example fix

// before
{"referenceValue": {"path": "users/u1"}}
// after
{"referenceValue": "users/u1"}

func checkReferencePayload(v any) error { if _, ok := v.(string); !ok { return fmt.Errorf("referenceValue payload must be a string, got %T", v) }; return nil }

func asReferenceString(v any) (string, bool) { s, ok := v.(string); return s, ok }

if _, err := JSONToFirestoreValue(val, client); err != nil {
    if strings.Contains(err.Error(), "reference value must be a string") { /* replace object/number payload with the path string */ }
}

When it happens

Trigger: Passing {"referenceValue": {"path": "users/u1"}} (object), {"referenceValue": 12345}, or {"referenceValue": null}.

Common situations: Clients serialize reference objects from another SDK instead of the raw path string; template engines emit null for unset references.

Related errors

• Toolbox binary not found
• HTTP error! status: ${response.status}
• Invalid number input for ${NAME}: ${RAW_VALUE}
• HTTP error ${response.status}: ${errorBody}
• Invalid JSON format for ${paramName}. Expected an array. ${e

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/455b00172dd4194a. Report an issue: GitHub.