Analyze an audio file. Modes:
- transcript: Speech-to-text with word-level timestamps — returns `{language, full_text, words}` where each word is `{word, start_ms, end_ms, punctuated_word}`. ⚠ MILLISECONDS here; get_clip's `voiceover_words` gives the same words in SECONDS as `{word, start, end}`. Use for caption timing, script editing, or word-level visual sync. Works on narration and on sung lyrics: the provider is picked from the content, and if it returns nothing the other one is tried automatically. So an empty `words` means the audio genuinely has no intelligible speech, not that the wrong engine ran.
- silences: returns `{silences, total_silence_ms}`, each span `{start_ms, end_ms, peak_db}`. Use for auto-trim, smart-split, or pause-aware editing.
- beats: returns `{tempo_bpm, beats_ms}` — beats_ms is an array of MILLISECOND positions. Empty for non-music. Use to align animations/zooms to a beat.
- features: returns `{duration_ms, peak_db, rms_db, lufs, has_music, has_speech, speech_share}` — loudness plus two INDEPENDENT hints — `has_music` (beats hold a steady period) and `has_speech` (at least 40% of the audible seconds sound like talking; `speech_share` is that share, 0-1). Instrumentals read false; so do sung vocals and narration under a loud bed, so when the words matter, use transcript. Cheap dispatcher — call once to pick a mode, or for duration_ms to pass as add_audio's source_duration.
- energy: loudness over time — `{samples_per_second, start_ms, db}`, db one RMS dBFS value per 1/samples_per_second s from start_ms (default 4 a second; energy_options.samples_per_second 1-20). Read builds, dips and hits from it.
- sections: how a track is built — `{loud_db, sections: [{label, start_ms, end_ms, db, onsets_per_s}], drops: [{t_ms, rise_db, quiet_start_ms?, quiet_end_ms?}]}`, label intro | build | drop | main | breakdown | outro; a drop's t_ms is the hit (within ~10 ms), quiet_* the dip just before it. Set animation cues on beats (beats mode) or drops.
- describe: what the audio IS — `{kind: speech|music|mixed, classification_confidence, duration_seconds, music?: {tempo_bpm, key, mood, genre, energy, instruments, description, suggested_search_query}, speech?: {...}}`. Pass suggested_search_query to find(type='music') for a similar track. Speech is not transcribed here; use transcript for the words.
Source: provide exactly one of mcp_upload_id (from upload tool) or file_url (already-public URL, e.g. a find(type='music') result or Clueso CDN file).
Optional time range: range_start_ms / range_end_ms crops the analysis window.