Head to head · Voice cloning · October 2026 research run

Gradium Voice Cloning and Voice Design vs Smallest.ai Instant Voice Clone

Gradium Voice Cloning and Voice Design scores 60.8 (C) on agent readiness against Smallest.ai Instant Voice Clone's 58 (C), and leads in 3 of 7 scored categories. Smallest.ai Instant Voice Clone leads on transparency & trust. Both do voice cloning.

Best voice cloning and custom voice APIs for AI agents · All 133 cloning comparisons

Which one, for what

Gradium Voice Cloning and Voice Design C

Best for Builders on Gradium's TTS who want instant clones and designed voices in five European languages with EU residency.

Ahead on

  • Schema & documentation, 83 against 70
  • Agent ergonomics, 67 against 62
  • Payments & pricing, 30 against 20

Also in its favour

  • Free to start without a card

Watch for

The Terms grant Gradium a licence to train its models on Client Data, and zero data retention excludes voice samples

Smallest.ai Instant Voice Clone C

Best for Teams already on Smallest's Lightning TTS or voice agents who want a clone from a short clip in one call.

Ahead on

  • Transparency & trust, 72 against 63

Watch for

The endpoint defaults to lightning-v3.1, whose clones stop working on 30 November 2026

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Schema & documentation Gradium Voice Cloning and Voice Design +13

Gradium Voice Cloning and Voice Design 83

Public OpenAPI 3.1 file at docs.gradium.ai/api-reference/openapi.json (25). llms.txt and Markdown pages (10). The guides say when to clone, design, enhance or localise a voice, and the custom-voice page explains the enhancement default and how to opt out (14 of 20). The clone body has audio_file, name and language required, a five-value language enum and typed defaults for start_s, enhance and timeout_s (14 of 15). curl and Python examples. The create call documents only 201 and 422, and the errors page covers synthesis, with plain-text 500 bodies (9 of 15). Routes carry no version, the OpenAPI file is 0.1.0, and release notes are dated per entry, newest 6 November 2026 (11 of 15). The API reference FAQ gives a 300-second session where the limits page says 3,000. 25+10+14+14+9+11 = 83.

Smallest.ai Instant Voice Clone 70

The API reference pages are generated with typed fields, enums and error schemas, but no OpenAPI file was found linked from the docs or llms.txt (5 of 25). llms.txt and a Markdown copy of every page (10). The guide says when to use the Pro pool, how to check modelIds before synthesis and why a mismatched clone returns empty audio, while the reference still names the retiring default (14 of 20). model and language are enums validated by the server, with required displayName and file, a 5 MB limit and MIME types listed, and tags as a comma-separated string (12 of 15). Examples in curl, Python and Node.js and a table of seven error cases with causes (14 of 15). Paths under /v1, a deprecation page with dated statuses and a models changelog with entries on 21, 24, 26, 28 and 29 October 2026 (15). 5+10+14+12+14+15 = 70.

Payments & pricing Gradium Voice Cloning and Voice Design +10

Gradium Voice Cloning and Voice Design 30

No x402, MPP or L402 (0). Plan prices and credits are public, 1 credit a character for speech, with no dollar price per unit, as cartesia-voice-cloning is read. Creating a clone uses no credits in the docs (10). The free plan has 45,000 credits a month, 5 custom voices and Voice Design, and the site says no credit card is required. Commercial use starts on the $12 plan (20). Signup is a browser flow in Gradium Studio (0). 0+10+20+0 = 30.

Smallest.ai Instant Voice Clone 20

No x402, MPP or L402 (0). Per-character TTS prices are public, about $0.175 per 10,000 characters on Lightning v3.1, but no price per clone is published and the models pricing table marks voice cloning No on pay as you go, against the docs (10). The agents pricing page states $10 in free credits, and whether a card is needed wasn't established (10 of 20). A person signs up in a browser and creates the key in the dashboard (0). 0+10+10+0 = 20.

Transparency & trust Smallest.ai Instant Voice Clone +9

Gradium Voice Cloning and Voice Design 63

Closed service with clear terms, version of 19 October 2026, naming Gradium SAS with its Paris registration (15 of 30). The Terms allow training on Client Data, zero data retention excludes voice samples, the privacy policy gives retention criteria without periods, and a DPA is published as an exhibit. The statements agree but give no retention period for samples (15 of 30). Deprecations appear in dated release notes, with no written notice policy (10 of 20). EU and US residency is documented and selectable from the XS plan. Sub-processors sit in the trust centre, not read (12 of 20). 15+15+10+12 = 52.

Smallest.ai Instant Voice Clone 72

Closed service with clear terms naming Smallest, Inc. under California law, effective 21 October 2026 (15 of 30). The Terms rule out training on customer content, the Privacy Policy (18 September 2026) gives retention criteria but no periods, and the Zero Data Retention page is specific about Enterprise options, with nothing on how long cloning samples are kept (16 of 30). A deprecation page with dated statuses (deprecated, rejects, removed, scheduled, retiring) and migration targets (16 of 20). Two regions named with locations. No sub-processor list was found and a DPA page exists unread (10 of 20). 15+16+16+10 = 57.

Agent ergonomics Gradium Voice Cloning and Voice Design +5

Gradium Voice Cloning and Voice Design 67

Voice objects are compact metadata (20 of 25). GET /voices/ takes skip and limit (default 100) and since 23 October filters by locale, gender and use_case (20). Validation errors are structured 422 bodies, while synthesis errors arrive as plain-text HTTP 500 with a numeric code to parse (12 of 20). No idempotency key. Saving a design candidate twice answers 409, and the clone call has none (5 of 20). Three required fields with sensible defaults, and one official SDK, in Python (10 of 15). 20+20+12+5+10 = 67.

Smallest.ai Instant Voice Clone 62

The clone response is a compact object with the voice ID, status and signed URLs to sample clips rather than inline audio (20 of 25). The list call returns every clone on the organisation with no pagination or filter found (10 of 20). Errors carry a message and, on 500, an error_code enum with a stated fix, such as retrying voice_clone_timeout (16 of 20). No idempotency key, and retrying a timeout can leave a duplicate clone, with deletion through an oddly named route (4 of 20). Two required fields. The Python SDK smallestai 5.14.0 is current, while the npm package smallestai was last published on 16 April 2025 (12 of 15). 20+10+16+4+12 = 62.

Score by category

CategoryWeight this runGradium Voice Cloning and Voice DesignSmallest.ai Instant Voice CloneEdge
Reliability16%206365Smallest.ai Instant Voice Clone +2
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28370Gradium Voice Cloning and Voice Design +13
Agent ergonomics13%16.26762Gradium Voice Cloning and Voice Design +5
Security & auth14%17.54848even
Payments & pricing10%12.53020Gradium Voice Cloning and Voice Design +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87072Smallest.ai Instant Voice Clone +2
Transparency & trust7%8.86372Smallest.ai Instant Voice Clone +9
Negative events≤1500
TotalC 60.8/100C 58/100

Facts side by side

FactGradium Voice Cloning and Voice DesignSmallest.ai Instant Voice Clone
KindModel APIModel API
VendorGradium SASSmallest, Inc.
Hosted endpointhttps://api.gradium.ai/api/voices/https://api.smallest.ai/waves/v1/voice-cloning
TransportsHTTP, websocketHTTP
AuthAPI keyAPI key
PricingFreemiumPay per use
Price for voice cloningnot published$17.50 per 1M characters
x402nono
LicenceProprietary service under Gradium's Terms of Service (version of 19 October 2026). The gradium Python SDK is on PyPIProprietary service under Smallest's Terms of Service. The smallestai Python SDK is on PyPI
Read-only variant documentednono
llms.txtyesyes
Last release2026-11-062026-10-29
Terms last updatedno date givenno date given
Privacy policy last updatedno date givenno date given
Customer content may train modelsyesnot found in the text
Terms restrict automated accessnot found in the textnot found in the text
Terms restrict benchmarkingnot found in the textnot found in the text
Terms or service can change without noticenot found in the textyes
Arbitration or class-action waivernot found in the textyes

Verdicts

Gradium Voice Cloning and Voice Design

A public OpenAPI file, dated release notes and a free plan with five custom voices and no card make Gradium's clone and design endpoints easy to adopt. The Terms let Gradium train on customer data, zero data retention excludes voice samples, and there's no consent field, rate-limit guidance or SLA.

Smallest.ai Instant Voice Clone

One multipart POST clones a voice from 5 to 15 seconds of audio and returns sample clips, with dated deprecation notices and current changelog entries. The endpoint still defaults to a model whose clones stop working on 30 November 2026, there's no consent field or clone price, and the status feed shows frequent short API outages.

Before you call either

Gradium Voice Cloning and Voice Design

  1. Send language on every clone. It's required and must be one of en, fr, de, es or pt and match the recording
  2. Clones are enhanced by default since 23 October 2026. Pass enhance=false to keep the raw voice, then check enhance on GET
  3. Pass a clone as voice_id in TTS, not voice
  4. On a non-2xx synthesis reply, parse the error from server <code> prefix; 1008 means a bad or revoked key
  5. Check the custom-voice allowance first. The free plan holds 5 voices shared by clones and designs

Smallest.ai Instant Voice Clone

  1. Always pass model=lightning-v3.1-pro. The default lightning-v3.1 clones stop working on 30 November 2026
  2. Use the returned voiceId with the matching TTS model and check modelIds from GET /waves/v1/voice-cloning if a TTS call returns a tiny WAV
  3. Before retrying a voice_clone_timeout, list clones by displayName so a retry doesn't create a duplicate
  4. Send the server API key, not an access token. The cloning endpoint refuses short-lived tokens
  5. Keep TTS calls from a clone to one at a time on the self-serve plan and back off on 429

Questions

Which is better for AI agents, Gradium Voice Cloning and Voice Design or Smallest.ai Instant Voice Clone?

Gradium Voice Cloning and Voice Design scores 60.8 (C) on agent readiness against Smallest.ai Instant Voice Clone's 58 (C), and leads in 3 of 7 scored categories. Smallest.ai Instant Voice Clone leads on transparency & trust.

Do Gradium Voice Cloning and Voice Design and Smallest.ai Instant Voice Clone need an API key?

Both need an API key.

Can an agent call Gradium Voice Cloning and Voice Design and Smallest.ai Instant Voice Clone without installing anything?

Yes. Gradium Voice Cloning and Voice Design has a hosted endpoint at https://api.gradium.ai/api/voices/ and Smallest.ai Instant Voice Clone at https://api.smallest.ai/waves/v1/voice-cloning.

Other comparisons with Gradium Voice Cloning and Voice Design or Smallest.ai Instant Voice Clone

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