[Bug]: mcp:test-tool crashes with “Array to string conversion” when JSON Schema type is an array (e.g., ["integer","null"])

[jhariani]

What happened?

This library is fantastic, thank you for all the work on it. One minor thing I ran into while testing: when a tool’s JSON Schema uses a union type, running:

php artisan mcp:test-tool tool_name --input='{"param":"value"}'

throws:

ErrorException

Array to string conversion

at vendor/opgginc/laravel-mcp-server/src/Console/Commands/TestMcpToolCommand.php:167
    163▕                 $type = $propSchema['type'] ?? 'any';
    164▕                 $description = $propSchema['description'] ?? '';
    165▕                 $required = in_array($propName, $schema['required'] ?? []) ? '(required)' : '(optional)';
    166▕
  ➜ 167▕                 $this->line("{$indent}- {$propName}: {$type} {$required}");

This happens because $type can be an array (e.g., ["integer","null"]) and is interpolated directly into a string.

How to reproduce the bug

Sample failing schema snippet:

"results_size" => [
    "description" => "The number of results to return. Defaults to 25.",
    "type"        => ["integer", "null"],
    "minimum"     => 0,
    "maximum"     => 500,
],

Command:

php artisan mcp:test-tool tool_name --input='{"param":"value"}'

Expected behavior

• The schema is printed without errors.
• Union types print cleanly, e.g., integer | null.
• Nested object/array properties are displayed even when type is a union such as ["object","null"] or ["array","null"].

Actual behavior

• Command crashes with “Array to string conversion” at line 167 in TestMcpToolCommand::displaySchema.

Proposed fix

Normalize type for display and separately detect whether the property is (or may be) an object or array. Also handle items.type being an array.

protected function displaySchema(array $schema, string $indent = ''): void
{
    if (!isset($schema['properties']) || !is_array($schema['properties'])) {
        return;
    }

    foreach ($schema['properties'] as $propName => $propSchema) {
        $typeRaw     = $propSchema['type'] ?? 'any';
        $description = $propSchema['description'] ?? '';
        $required    = in_array($propName, $schema['required'] ?? [], true) ? '(required)' : '(optional)';

        // Normalize type for display (string) and detection (array)
        $typeList = is_array($typeRaw) ? $typeRaw : [$typeRaw];
        $typeList = array_values(array_filter($typeList)); // tidy
        $typeForDisplay = $typeList ? implode(' | ', $typeList) : 'any';

        $this->line("{$indent}- {$propName}: {$typeForDisplay} {$required}");
        if ($description) {
            $this->line("{$indent}  Description: {$description}");
        }

        // Determine if the schema includes object/array among union types
        $isObject = in_array('object', $typeList, true);
        $isArray  = in_array('array', $typeList, true);

        // If this is an object with nested properties
        if ($isObject && isset($propSchema['properties']) && is_array($propSchema['properties'])) {
            $this->line("{$indent}  Properties:");
            $this->displaySchema($propSchema, $indent . '    ');
        }

        // If this is an array with items
        if ($isArray && isset($propSchema['items']) && is_array($propSchema['items'])) {
            $itemsTypeRaw = $propSchema['items']['type'] ?? 'any';
            $itemsTypeList = is_array($itemsTypeRaw) ? $itemsTypeRaw : [$itemsTypeRaw];
            $itemsTypeForDisplay = $itemsTypeList ? implode(' | ', $itemsTypeList) : 'any';

            $this->line("{$indent}  Items: {$itemsTypeForDisplay}");

            // Array items might themselves be objects with properties
            if (isset($propSchema['items']['properties']) && is_array($propSchema['items']['properties'])) {
                $this->line("{$indent}  Item Properties:");
                $this->displaySchema($propSchema['items'], $indent . '    ');
            }
        }
    }
}

Package Version

1.4.2

PHP Version

8.4.11

Laravel Version

11.45.2

Which operating systems does this happen with?

Linux, macOS

Notes

No response