Rime TTS API + MCP by Rime Labs

# Fix list: Rime TTS API + MCP

From Anchor Terminal's listing at https://www.anchorterminal.com/tools/rime-tts, the October 2026 research run, assessed 1 October 2026. Grade C, 56.1 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 Rime TTS API + MCP: 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. Reliability, 50 out of 100, up to 10 more on the total

Why it scored 50: Status page at status.rime.ai runs Uptime Kuma, which shows live monitors but no incident archive, and it needs JavaScript we couldn't run (10 of 20). No readable incident history, so we can't judge the last 90 days (5). Starter allows 20 concurrent TTS generations, but WebSocket connection limits aren't published (10 of 15). The errors page says to back off on 429 and retry the upgrade after a delay, marks 500 and 502 as retryable and warns that retries bill as new synthesis (15). SLAs are an Enterprise item, none published (0). Coda and Mist v3 are GA (10).

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

Hosted APIs, MCP servers, models and platforms.

- 20, a public status page with component history (Statuspage, Instatus, BetterStack or the vendor's own).
- 0 to 30, the incident record for the last 90 days on that page. 30 for a clean record or trivial incidents only, 20 for minor incidents only, 10 for one major outage (an hour or more of a core API down, or errors across the board), 0 for several. 5 when there's no history we could read, and the note says so.
- 15, rate limits documented with numbers.
- 15, documented 429 or overload handling (Retry-After, backoff guidance), and idempotency keys or safe-retry guidance where writes are involved.
- 10, an SLA published for any paid tier.
- 10, the surface agents use is generally available, not beta or preview.

Local packages, SDKs, frameworks and stdio MCP servers.

- 20, installs from an official package with supported runtimes stated.
- 25, a public CI and test suite, passing on the default branch.
- 0 to 25, open crash or regression issues relative to activity (25 for few and handled, 0 for many, old and unanswered).
- 15, semver discipline and breaking changes called out in a changelog.
- 15, version 1.0 or later, or declared stable.

Protocols are read from their reference implementations, the public facilitators or servers, spec stability and test vectors.

## 2. Payments & pricing, 40 out of 100, up to 7.5 more on the total

Why it scored 40: No x402, MPP or L402 (0). Coda $0.05 and Mist v3 $0.03 per 1,000 characters, published without a login (20). Free usage on Starter with no card. The FAQ says 3,000 minutes, while last week's check found about 800 minutes elsewhere on the page (20). A person signs up in a browser (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.

## 3. Schema & documentation, 59 out of 100, up to 6.7 more on the total

Why it scored 59: No OpenAPI or AsyncAPI file found (0). llms.txt with Markdown pages (10). The models page says which model suits what, and that a request without `modelId` goes to Mist v3 (15 of 20). Parameters are typed in reference tables, but there's no machine-readable schema to check enums against (10 of 15). Examples on each endpoint and an errors page listing the messages for each status, as plain text (12 of 15). Dated changelog and versioned WebSocket paths (`/ws3`, `/ws2`), no API version header (12 of 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.

## 4. Agent ergonomics, 60 out of 100, up to 6.5 more on the total

Why it scored 60: API reading of the checklist. MP3, WAV, Opus, PCM and mu-law from 8 to 96 kHz, chosen by `Accept`, with word timestamps on `/ws3` (22 of 25). HTTP requests stop at 1,000 characters and the WebSocket buffers by sentence, but no voice-list paging or filters found in the API (12 of 20). Errors are plain-text messages, 11 for validation and 5 for auth, with no machine-readable codes, and WebSocket failures arrive as close code 1011 with the reason in a string (12 of 20). Clear retry guidance, and the docs say retries are billed (10 of 20). Two required fields, but the default model breaks Coda speakers, and there are no official SDKs (4 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. Security & auth, 65 out of 100, up to 6.1 more on the total

Why it scored 65: Model reading of the checklist, with training and retention in place of least-privilege and injection lines. One Bearer key per request, sent as a header on WebSockets too, with no scopes or short-lived tokens, so browser apps need a server bridge (20 of 30). Customer data isn't used for training unless the customer opts in (20). Only character counts are kept by default, and request retention for support is an off-by-default dashboard switch since 2026-08-25 (15). No per-call log found (0 of 15). SOC 2 Type II since May 2025 and a HIPAA BAA on request. No security.txt, disclosure policy or bug bounty found (10 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.

## 6. Maintenance & community, 48 out of 100, up to 4.6 more on the total

Why it scored 48: Read as a model. Changelog entry on 2026-09-25 and release `20260912` with a new Coda checkpoint (30). Seven dated entries in the last 90 days (10). Arcana's cloud retirement was announced on 2026-07-29 and took effect on 2026-08-15, 17 days later, with traffic routed to Coda (0 of 10). Public changelog and a support address (8 of 15). No official SDK repository to judge (0 of 10). No official SDKs (0). No package to check (0).

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.

## 7. Transparency & trust, 71 out of 100, up to 2.5 more on the total

Made of editorial 55, provenance 86.

Why it scored 71: Closed service with clear terms (15). The privacy page and the changelog agree on character counts only, no training without opt-in and optional retention off by default, but no retention period or named sub-processors (22 of 30). Arcana's retirement is dated in the changelog, with no written policy and 17 days' notice (10 of 20). Cloud in US West and US East plus VPC and on-prem, no sub-processor list found (8 of 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):

- Domain age: rime.ai, registered 2020-03-12 (6 years) (11 of 15)
- security.txt: not found (0 of 10)

## 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.

- How many free minutes a new account gets. The FAQ says 3,000 and last week's check found about 800 elsewhere on the page.
- Whether Coda covers 8 or 9 languages. The 2026-08-04 changelog says 8 and the listing says 9.
- The incident history behind status.rime.ai, which needs JavaScript.

## Weaknesses

- No OpenAPI or AsyncAPI file and no official SDKs
- Errors are plain-text messages without machine-readable codes
- Arcana's cloud retirement came 17 days after the announcement
- Status page shows no incident history
- HTTP requests stop at 1,000 characters

## 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.

- Always send `modelId`, since a missing one routes to Mist v3 and Coda speakers then fail.
- Keep HTTP requests under 1,000 characters or use the WebSocket.
- Back off on 429 before reopening a WebSocket, and remember each retry bills again.
- Use `/ws3` when you need word timestamps.
- Keep the key server-side, since WebSockets take it in a header and there are no short-lived tokens.

## What the review panel asked for

- Fix the free minutes figure
- publish WebSocket connection limits
- keep an incident archive

## 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.