Amazon Polly by Amazon Web Services

# Fix list: Amazon Polly

From Anchor Terminal's listing at https://www.anchorterminal.com/tools/amazon-polly, the October 2026 research run, assessed 1 October 2026. Grade BB, 75.8 out of 100.

This is everything the published grade says the listing lacks, the biggest possible gain to the total first. It comes from the reason given for each score, the checklist each category was scored against (https://www.anchorterminal.com/benchmark/#checklist), the provenance checks, the deductions, what we couldn't check and what the review panel asked for. A fix counts at the next check, once it's public.

For a coding agent working on Amazon Polly: work through the items below in the product, its docs and its public pages. Each category gives the reason for its score, with the points each checklist item earned, and the checklist itself, so the gap is the items that earned less than their points. Change the product, not the wording, and keep a note of what you changed and where it's published.

## 1. Payments & pricing, 20 out of 100, up to 10 more on the total

Why it scored 20: No x402, MPP or L402 (0). Per-1M-character prices for each engine published without a login (20). A new AWS account needs a card, and the monthly free characters apply only to accounts opened before 2025-07-15 (0). A person signs up in a browser. IAM can mint keys by API, but only after a human has an account (0).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-payments):

The published rubric, also on the [x402 page](https://www.anchorterminal.com/x402/).

- 40, a machine payment protocol (x402, MPP or L402) on the tool's own endpoints. 10 to 30 when it covers only some endpoints or only goes through a third party, and the note says which.
- 20, per-call or per-unit pricing published without a login. 10 for public plan-only pricing, 0 for "contact sales" or prices behind a login.
- 20, a free tier or trial that doesn't need a card.
- 20, autonomous onboarding, meaning an agent can get access without a person signing up in a browser (keyless use, x402, a programmatic key API).

Payment platforms and agent wallets rarely charge for their own API over a machine protocol, so the first line has steps for them, and the highest one that applies counts. 40 when x402, MPP or L402 runs on all their own endpoints, 30 when it runs on part of their own API, 25 when their merchants can accept one, 20 for running a facilitator, 15 for paying as a buyer, and 0 when the only protocol is their own. Merchant acceptance sits above a facilitator because the platform's own customers can charge agents through it, while a facilitator settles for sellers who wire up the protocol themselves. The counter-argument (a facilitator does more for the protocol as a whole) has a point. Each note says which step applied.

Open-source software you run yourself is scored on its hosted or paid option if it has one. A free, self-hosted package with nothing to buy gets 20, 20 and 20 for the last three lines, and 0 to 40 for the first only if it ships a payment protocol.

## 2. Maintenance & community, 50 out of 100, up to 4.4 more on the total

Why it scored 50: Read as a model. The newest service change in the document history is 2026-08-12, generative voices and bidirectional streaming in Sydney. The 2026-09-15 entry only clarifies CloudWatch metric descriptions (20). Two dated entries in the last 90 days (0 of 10). No deprecation policy or dated notices for voices or engines found. The dated deprecations are for the WordPress and SAPI plugins in 2023 (0 of 10). Public document history, AWS re:Post and paid support plans, SDK issue trackers not checked (10 of 25). Official SDKs current in Python, JavaScript, Java, Go and others (15). SDK package health not checked (5 of 10).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-maintenance):

- 0 to 30, time since the last release, or the last published model or API change for a closed service. 30 within 30 days, 20 within 90, 10 within 180, 0 older.
- 20, at least three releases or dated changelog entries in the last 90 days.
- 0 to 25, responsiveness. Issues and pull requests answered on GitHub (the open issues and how recent the replies are). For closed services, a public changelog and a support or community channel that answers, 0 to 15.
- 15, presence in the official MCP registry under a verified namespace (MCP servers), or current official SDKs (APIs and models).
- 10, package health, current dependencies and CI.

Models are read for deprecation notice periods and model churn rather than release counts.

## 3. Security & auth, 80 out of 100, up to 3.5 more on the total

Why it scored 80: Model reading of the checklist, with training and retention in place of least-privilege and injection lines. SigV4 with IAM users, roles and temporary credentials, scoped per action and resource by policy (30). AWS may store and use text processed by Polly to improve the service by default, and any customer can opt out with an AI services opt-out policy in `AWS Organizations` (10 of 20). Synchronous output streams back and async output goes to your own bucket, but stored input isn't zero-retention by default (10 of 15). CloudTrail logs API calls per caller (15). Vulnerability reporting policy, SOC and ISO reports in AWS Artifact, public security bulletins. The security.txt on aws.amazon.com passed its Expires date on 2026-09-24 and we found no paid public bug bounty (15 of 20).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-security):

- 0 to 30, the credential model. 30 for OAuth 2.1 with scopes, or scoped and revocable keys with rotation. 20 for plain revocable API keys. 10 for one all-powerful key. 10 off when a secret can travel in a URL query string as a documented option.
- 0 to 20, read-only or least-privilege modes, and confirmation or approval for destructive actions.
- 0 to 15, prompt-injection posture where the tool returns untrusted content (documented mitigations or guidance). A tool that returns no untrusted content gets 10.
- 0 to 15, audit logs or per-call visibility for the operator.
- 0 to 20, a security programme. security.txt or a disclosure policy, a bug bounty, SOC 2 or ISO 27001, advisories handled in public.

Models are read for retention, whether API data trains models (and whether that's off by default), zero-retention options and certifications. Frameworks for telemetry defaults, approval hooks, guardrails and sandboxing.

## 4. Agent ergonomics, 82 out of 100, up to 2.9 more on the total

Why it scored 82: API reading of the checklist. MP3, Ogg Vorbis or PCM at chosen sample rates, or speech marks as JSON instead of audio, and async tasks that write to your S3 bucket (22 of 25). `DescribeVoices` filters by engine and language and pages with `NextToken`, task lists page with `MaxResults`, and per-request limits are published (3,000 billed characters, 10 minutes of audio) (20). Typed exceptions per action such as `TextLengthExceededException`, `InvalidSsmlException` and `EngineNotSupportedException` (20). Backoff guidance and stateless synthesis, but no idempotency token on async tasks (10 of 20). Three required fields, SigV4 signing adds work without an SDK, SDKs in every major language (10 of 15).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-ergonomics):

- 0 to 25, context cost. For MCP, the number and size of the tool definitions (25 for ten or fewer compact tools, 15 for 11 to 30, 5 for more than 30, plus up to 10 back for toolsets, dynamic loading or read-only subsets). For APIs, whether responses can be sized (field selection, limits, summaries).
- 20, pagination, filtering and output-size controls.
- 20, actionable, documented error responses, codes and messages an agent can recover from.
- 20, idempotency or safe retries, and for MCP the `readOnlyHint` and `destructiveHint` annotations.
- 15, sensible defaults, few required parameters, and official SDKs in at least two languages.

Models are read for tool use, structured output, prompt caching, context length, batch and SDKs. Frameworks for how much code and how many defaults a tool-calling agent with MCP needs.

## 5. Transparency & trust, 80 out of 100, up to 1.8 more on the total

Made of editorial 65, provenance 95.

Why it scored 80: Closed service under the AWS Service Terms (15). The service terms, privacy notice and Polly guide agree, a data processing addendum and a public sub-processor list exist, but the default permission to use content sits in the service terms rather than the Polly guide (25 of 30). Plugin deprecations are dated in the document history, nothing for the API itself (5 of 20). Sub-processors and regions disclosed, with the region chosen per request (20).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-transparency):

- 0 to 30, source availability and licence clarity. 30 for open source under an OSI licence, 15 for closed with clear terms, 0 for unclear terms.
- 0 to 30, data handling and retention statements that agree with each other (privacy policy, DPA, retention periods, subprocessors).
- 0 to 20, a deprecation policy or notices with dates.
- 0 to 20, telemetry disclosed with an opt-out (local software), or subprocessors and data locations disclosed (hosted).

The other half of Transparency and trust is the provenance score, computed from checked facts (below). The category score is the mean of the two.

Provenance checks not met in full (half of this category, computed from checked facts):

- security.txt: published but past its Expires date (5 of 10)

## 6. Schema & documentation, 90 out of 100, up to 1.6 more on the total

Why it scored 90: The service model is public in the AWS SDKs (botocore and the JavaScript v3 clients), a machine-readable contract in the role OpenAPI plays (25). llms.txt for the developer guide (10). The engine pages say which engine suits short prompts, long-form reading and conversational speech (15). Inputs typed with enums for `Engine`, `OutputFormat`, `TextType` and `VoiceId`, required fields marked (15). Every action lists its errors with HTTP codes, but the API reference pages have no examples, which live in the developer guide (10). API version 2016-06-10 and a dated document history (15).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-schema):

APIs and MCP servers.

- 25, a machine-readable contract (a public OpenAPI file or similar; for MCP, typed JSON Schema inputs on every tool).
- 10, llms.txt or Markdown docs served for agents.
- 0 to 20, descriptions that say what a tool is for, when to use it and when not to, read from the tool definitions in the source or the API reference.
- 0 to 15, typed inputs with enums, constraints and required fields, and no free-form JSON blobs.
- 0 to 15, examples and documented error responses.
- 15, versioning and a public changelog.

Models are read from the API reference, the OpenAPI file, llms.txt, the structured-output and tool-use docs and the model cards. Frameworks from docs a model can follow, typed interfaces, examples and the API reference.

## What we couldn't check

What we couldn't read counted as absent. Publishing it on a page a plain HTTP fetch can read (not only in a browser) lets the next check count it.

- The patch moves `lastRelease` to 2026-08-12, the newest service change in the document history. The old 2026-09-29 date matched no entry we found and may have been an SDK build.
- The listing said Sydney got generative voices on 2026-09-15. The document history dates that to 2026-08-12, and 2026-09-15 is a CloudWatch documentation fix. The patch corrects `notable`.
- We read only the us-east-1 status feed.

## Weaknesses

- AWS may store and use text to improve the service unless the organisation sets an AI services opt-out policy
- A new account needs a card, and the monthly free characters only apply to accounts opened before 2025-07-15
- Neural, long-form and generative synthesis is limited to 8 requests a second by default
- Generative voices support only part of SSML
- No dated service change since 2026-08-12

## What costs an agent a turn today

The notes we give agents before they call it. Each one is a workaround an agent shouldn't need.

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

## What the review panel asked for

- card-free trial
- Idempotency token on async tasks
- Per-account opt-out
- dated notice before a voice or engine is retired
- Examples in the reference
- Machine-readable availability list
- examples in the API reference
- per-account opt-out
- no default content use
- One free tier for all accounts
- Return 429 with Retry-After
- Publish time to first audio

## When it's done

Send what changed and where it's published as a dispute (https://www.anchorterminal.com/builders/#disputes, or `POST https://www.anchorterminal.com/api/v1/contact` with `"kind": "dispute"`). Disputes are answered in public, and the listing is checked again by the same checklist. Paying for an audit or a listing claim changes nothing here.