Loudly Music API by Loudly GmbH

# Fix list: Loudly Music API

From Anchor Terminal's listing at https://www.anchorterminal.com/tools/loudly, the October 2026 research run, assessed 1 October 2026. Grade E, 38.5 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 Loudly Music API: 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, 15 out of 100, up to 17 more on the total

Why it scored 15: No status page found (0). No readable incident history (5). No rate limits with numbers, only a note that paid plans get higher limits (0). The OpenAPI spec documents 402 for insufficient credits but no 429, Retry-After or backoff guidance (0). No SLA (0). The API is versioned 1.0.0 and isn't labelled beta (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. Security & auth, 35 out of 100, up to 11.4 more on the total

Why it scored 35: A plain key from the self-serve developer portal in an `API-KEY` header, with no scopes, rotation or expiry documented (20). No least-privilege or read-only mode (0). Returns generated audio and catalogue metadata from Loudly's own library, no untrusted content (10). A credits endpoint shows the balance, with no per-call log found (5). No security.txt, disclosure policy, bug bounty or certification found (0).

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.

## 3. Payments & pricing, 30 out of 100, up to 8.8 more on the total

Why it scored 30: No x402, MPP or L402 (0). The developer pricing page lists subscription tiers from $0.15 a track at 500 tracks a month to $0.071 at 50,000, while the pay-as-you-go per-track price shows only after sign-in. That page didn't render for us on 2026-10-01, so this relies on the listing's check of 2026-09-30 (10). A new key comes with a free track allowance on sign-up, with no card step described, and `test=true` calls are free (20). A person signs up on the developer portal (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.

## 4. Maintenance & community, 3 out of 100, up to 8.5 more on the total

Why it scored 3: No dated release, changelog entry or API change found (0). No dated entries in the last 90 days (0). No public changelog. Support is help@loudly.com (3). No official SDK (0). No package to judge (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.

## 5. Agent ergonomics, 51 out of 100, up to 8 more on the total

Why it scored 51: Responses are JSON with track URLs (15) and duration is a parameter, but we found no output format choice in the spec (5). List endpoints take `page` and `limit` and return page metadata (10). Error payloads name the cause, including 402 for credits and 403 when the Manta flag is off, with no 429 documented (15). No idempotency key or retry guidance, and `test=true` helps wiring but not retries (0). Genre, BPM and instrument values must match the genres endpoint, and requests are multipart form data (6). No official SDK (0).

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.

## 6. Schema & documentation, 75 out of 100, up to 4.1 more on the total

Why it scored 75: Public OpenAPI 3.0 spec covering 19 paths across account, catalogue, generation, Manta, remix, mastering and stems (25). The site has an llms.txt, but it only links to the Music API page, with no agent-facing API docs (5). Every operation carries a description, though few say when not to use one (14). Enums for energy, key root and quality, model version (`VEGA_1`, `VEGA_2`) and stem model, a 30 to 420 second range for duration, and genres fetched from an endpoint rather than enumerated in the spec (13). Error schemas with example payloads for 400, 402, 403, 404 and 500 (13). Version 1.0.0 in the spec, no public changelog (5).

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.

## 7. Transparency & trust, 56 out of 100, up to 3.9 more on the total

Made of editorial 42, provenance 70.

Why it scored 56: Closed service with terms and a royalty-free, perpetual, worldwide licence for output, with a legal guarantee on the API page and indemnity for subscription partners per the pricing page (15). The privacy policy (updated 2024-03-07) keeps data as long as each purpose needs, with no fixed periods, and we found no DPA. Training-data claims sit in marketing copy, not in the policy (12). No deprecation policy or dated notices (0). The privacy policy names processors and locations, including Google and AWS in the US, Brevo (SendinBlue) in France and Shopify in Canada, though it reads as written for the consumer app (15).

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):

- Status page: not found (0 of 10)
- Changelog: not found (0 of 10)
- 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.

- The developer pricing page didn't render for us on 2026-10-01, so the per-track tiers rest on the listing's check of 2026-09-30.
- We found no output format parameter in the spec, so whether MP3 or WAV can be chosen is unconfirmed.
- Loudly's training-data claims (consented dataset, no training on uploads) weren't readable in the llms.txt we fetched today.
- Whether failed generations or `test=true` calls count against rate limits isn't documented.

## Weaknesses

- No status page, changelog, rate limits or 429 guidance
- One unscoped key per account, and no security.txt or disclosure policy
- Vocals and 12-stem splits need Loudly to switch on account flags
- No official SDK, and requests are multipart form data

## 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.

- Send `test=true` while wiring up. It returns a dummy song and spends no credits
- Call `GET /api/ai/genres` first. Genre, BPM range and instrument names must match that list
- Treat 402 as out of credits and stop, not retry
- A 403 on Manta routes means the account flag is off, not a bad key

## What the review panel asked for

- Self-serve Manta access
- A 429 with Retry-After
- Publish the pay-as-you-go price

## 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.