The default value for the channel parameter is auto. When enabled, APIPASS automatically allocates tasks across available providers based on real-time pricing and stability metrics to balance minimal cost and reliable performance. starter is ultra-low-cost with limited quotas and weaker stability; regular is standard and much cheaper than official APIs with moderate stability; official uses the model native API with high stability, fast task execution, and official pricing.

Validation uses text.strip() to reject empty text, but the original text is sent upstream without trimming. Billing uses len(text) on the raw string, so spaces, newlines, and punctuation count toward character usage. Text longer than 5000 characters is not split automatically; split long text into multiple tasks yourself.

Voice names are case-sensitive exact values. Variants such as rachel or RACHEL are not converted automatically and unsupported voices do not silently fall back to Rachel.

Must be a JSON number. Integers 0 and 1 and valid floating-point values are accepted and converted to float before sending upstream. JSON booleans, numeric strings such as "0.5", NaN, and infinity values are rejected.

When true, the upstream provider may return an additional timestamp JSON file alongside the audio file. The unified ApiPass resultJson extracts file URLs into resultUrls and does not retain each upstream file_type, so clients should handle multiple URLs and identify audio versus JSON by content or suffix.

Must be a string. The input is trimmed and lowercased before validation, so " ON " is normalized to "on". Other values return a parameter error and do not fall back to the default.