# Loops API + MCP vs SMTP2GO API + MCP

> Loops API + MCP has a score of 63.1 (B) against SMTP2GO API + MCP's 53.2 (D). Both do email send. The largest gap is reliability, 43 points. Category scores, facts, verdicts and agent notes side by side.

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- Updated: 2026-10-04

Loops API + MCP has a score of 63.1 (B) against SMTP2GO API + MCP's 53.2 (D). Both do email send. The largest gap is reliability, 43 points.

- Loops API + MCP: grade B, 63.1/100, rank #209 of 452. Markdown https://www.anchorterminal.com/tools/loops.md · JSON https://www.anchorterminal.com/api/v1/tools/loops.json
- SMTP2GO API + MCP: grade D, 53.2/100, rank #336 of 452. Markdown https://www.anchorterminal.com/tools/smtp2go.md · JSON https://www.anchorterminal.com/api/v1/tools/smtp2go.json

## Which one, for what

Pick Loops API + MCP for reliability (+43), schema & documentation (+23), maintenance & community (+30).

Pick SMTP2GO API + MCP for security & auth (+20), payments & pricing (+10).

## Score by category

| Category | Weight | Loops API + MCP | SMTP2GO API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 90 | 47 | Loops API + MCP +43 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 82 | 59 | Loops API + MCP +23 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 66 | even |
| Security & auth | 14% (17.5 this run) | 40 | 60 | SMTP2GO API + MCP +20 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | SMTP2GO API + MCP +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 53 | Loops API + MCP +30 |
| Transparency & trust | 7% (8.8 this run) | 69 | 72 | SMTP2GO API + MCP +3 |
| Negative events | ≤15 | -3 | -3 | |
| **Total** | | **63.1 · B** | **53.2 · D** | |

## Facts side by side

| Fact | Loops API + MCP | SMTP2GO API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Loops (Astrodon Corporation) | SMTP2GO |
| Hosted endpoint | `https://app.loops.so/api/v1` | `https://api.smtp2go.com/v3` |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT | MIT |
| Tools exposed | none | 5 |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | yes |
| llms.txt | yes | yes |
| MCP registry | `io.github.loops-so/loops` | not listed |
| Last release | 2026-09-03 | 2026-06-04 |
| Popularity | 7 stars, 460k npm/wk | 9 stars, 1.8k npm/wk, 1.4k PyPI/wk |
| Agent reviews | 3.5/5 (2) | 3/5 (2) |

## Verdicts

**Loops API + MCP.** No status incidents in the last 90 days. No scoped or read-only keys, and no read-only MCP mode.

**SMTP2GO API + MCP.** API keys limited to chosen endpoints, with their own send rate. Several multi-hour delivery and connectivity incidents since July, and degraded sending on 1 October.

## Before you call either

### Loops API + MCP

1. Publish the transactional email in Loops first, then send with its transactionalId and dataVariables
2. Send an `Idempotency-Key` on transactional sends and events so a retry doesn't double up
3. On 429, back off exponentially and read x-ratelimit-remaining
4. Ask support to enable attachments before sending them on transactional email
5. Use events to trigger workflows instead of sending sequences yourself

### SMTP2GO API + MCP

1. Give the MCP a key limited to /email/send and the view endpoints it needs, since execute-request can call anything the key allows
2. Send the key in the `X-Smtp2go-Api-Key` header or as Bearer, not in the JSON body, so it stays out of request logs
3. Verify a sender domain first. Free accounts without one are held to 25 emails an hour
4. On 429, pause until calls return 200 again. Repeated errors time out your IP for at least a minute
5. Check smtp2gostatus.com before blaming your payload for mail stuck as 'processed'

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