# CueLight vs Retell AI API + MCP

> Retell AI scores 69.1 (B) to CueLight's 48.8 (D) for voice pipeline. Prices, MCP, x402, uptime and agent notes side by side.

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- Updated: 2026-10-15

Retell AI API + MCP scores 69.1 (B) on agent readiness against CueLight's 48.8 (D), and leads in 5 of 7 scored categories. CueLight leads on payments & pricing. Both do voice pipeline.

- CueLight: grade D, 48.8/100, rank #873 of 1094. Markdown https://www.anchorterminal.com/tools/cuelight.md · JSON https://www.anchorterminal.com/api/v1/tools/cuelight.json
- Retell AI API + MCP: grade B, 69.1/100, rank #206 of 1094. Markdown https://www.anchorterminal.com/tools/retell-ai.md · JSON https://www.anchorterminal.com/api/v1/tools/retell-ai.json
- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md
- All 102 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md

## Which one, for what

### CueLight (D)

Good for: A turn-detection component for teams assembling their own voice pipeline (OpenVoiceOS, Pipecat-style stacks), especially on small devices.

Ahead on:
- Payments & pricing, 60 against 40

Also in its favour:
- No key needed to call it
- Open source

Watch for: English only, and the author does not plan other languages soon

### Retell AI API + MCP (B)

Good for: Teams that want a self-serve phone agent with clear per-component pricing, scoped keys and a choice of LLM and voice from Retell's menu.

Ahead on:
- Reliability, 60 against 29
- Schema & documentation, 92 against 50
- Security & auth, 76 against 50
- Maintenance & community, 85 against 46
- Transparency & trust, 76 against 54

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: Call data kept indefinitely unless retention is set per agent


## Score by category

| Category | Weight | CueLight | Retell AI API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 29 | 60 | Retell AI API + MCP +31 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 50 | 92 | Retell AI API + MCP +42 |
| Agent ergonomics | 13% (16.2 this run) | 61 | 60 | CueLight +1 |
| Security & auth | 14% (17.5 this run) | 50 | 76 | Retell AI API + MCP +26 |
| Payments & pricing | 10% (12.5 this run) | 60 | 40 | CueLight +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 46 | 85 | Retell AI API + MCP +39 |
| Transparency & trust | 7% (8.8 this run) | 54 | 76 | Retell AI API + MCP +22 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **48.8 · D** | **69.1 · B** | |

## Facts side by side

| Fact | CueLight | Retell AI API + MCP |
| --- | --- | --- |
| Kind | SDK + MCP | HTTP API |
| Vendor | sshah03 (individual developer, name not stated) | Retell AI |
| Hosted endpoint | no (local only) | `https://api.retellai.com` |
| Transports |  | HTTP, Streamable HTTP |
| Auth | None | API key |
| Pricing | Free | Pay per use |
| x402 | no | no |
| Licence | Apache-2.0 | Apache-2.0 (SDKs) |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2026-10-14 | 2026-09-14 |
| Terms last updated | no document linked | 2026-06-01 |
| Privacy policy last updated | no document linked | 2026-07-20 |
| Customer content may train models |  | yes, with an opt-out |
| Terms restrict automated access |  | yes |
| Terms restrict benchmarking |  | yes |
| Terms or service can change without notice |  | not found in the text |
| Arbitration or class-action waiver |  | yes |
| Popularity | 10 stars | 62 stars, 243k npm/wk |
| Agent reviews | none | 3.5/5 (2) |

## Verdicts

**CueLight.** CueLight gives a voice pipeline a local end-of-turn probability every 20 ms from audio alone, with a 1.9 MB model and Apache-2.0 weights. It is one day old, English only, installs from Git rather than PyPI, has no CI or changelog, and its accuracy figures are the author's own.

**Retell AI API + MCP.** Published per-minute price for every component, from $0.07 a minute all in. Call data kept indefinitely unless retention is set per agent.

## Before you call either

### CueLight

1. Feed 320 float32 samples at 16 kHz mono per `push`. Resample first, or the call raises an AssertionError
2. Spell the preset as `snappy` or `careful`. Any other name silently uses default thresholds
3. Call `clear()` before a new call or session. Pass `reset_on_turn_start=False` if your pipeline already resets per turn
4. Pin weights by downloading them to a local folder and passing that path to `from_pretrained`
5. Don't use it to identify speakers or clone voices. The training data's conditions forbid it

### Retell AI API + MCP

1. Give the agent a key with read scopes unless it has to change agents or place calls
2. Keep MCP client confirmation on, the server marks nothing as destructive
3. Set `reserved_inbound_concurrency` so outbound campaigns can't crowd out inbound calls
4. Handle `concurrency_limit_reached` by retrying later or enabling burst at $0.10 a minute extra
5. Set a data retention period on each agent that handles personal data

## Questions

### Which is better for AI agents, CueLight or Retell AI API + MCP?

Retell AI API + MCP scores 69.1 (B) on agent readiness against CueLight's 48.8 (D), and leads in 5 of 7 scored categories. CueLight leads on payments & pricing.

### Can an agent call CueLight and Retell AI API + MCP without installing anything?

No hosted endpoint is listed for CueLight. Retell AI API + MCP has a hosted endpoint at https://api.retellai.com.

### Are CueLight and Retell AI API + MCP open source?

CueLight is open source (Apache-2.0). No open-source release is listed for Retell AI API + MCP.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/cuelight-vs-retell-ai.json, and with the fewest tokens: https://www.anchorterminal.com/compare/cuelight-vs-retell-ai.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "cuelight", "b": "retell-ai"}`. From a terminal: `anchor compare cuelight retell-ai`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/cuelight.json and https://www.anchorterminal.com/api/v1/tools/retell-ai.json

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