Amazon Polly vs ElevenLabs Text to Speech API + MCP

Amazon Polly

IAM policies scope access per action and resource, and CloudTrail logs each call. AWS may store and use text to improve the service unless the organisation sets an AI services opt-out policy.

ElevenLabs Text to Speech API + MCP

Keys can be limited to chosen endpoints and given a credit quota, and service accounts hold keys that don't belong to a person. Content may be used for training unless you opt out under Data use, and the opt-out only applies going forward.

Amazon Polly

1. Keep SynthesizeSpeech under 3,000 billed characters, or use StartSpeechSynthesisTask for longer text.
2. Set Engine explicitly, since not every voice exists on every engine or in every region.
3. Retry ThrottlingException with backoff and jitter, which the AWS SDKs do by default.
4. Check the generative SSML tag list before porting neural SSML.
5. Ask for OutputFormat json with speech marks when you need word timings.

ElevenLabs Text to Speech API + MCP

1. Call Eleven v4 through Text to Dialogue, not /v1/text-to-speech.
2. Spell out numbers yourself on eleven_flash_v2_5, which doesn't normalise them by default, and turning that on is Enterprise only.
3. On 429 read code, back off on rate_limit_exceeded and wait for running requests on concurrent_limit_exceeded.
4. Keep each request under 10,000 characters on v4 and Multilingual v2, 5,000 on v3.
5. Give the agent a key scoped to Text to Speech with a credit quota.