# Groundmail API + MCP vs Loops API + MCP

> Loops scores 62.7 (B) to Groundmail's 57.6 (C) for sending email. Prices, MCP, x402, uptime and agent notes side by side.

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- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
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- Updated: 2026-10-17

Loops API + MCP scores 62.7 (B) on agent readiness against Groundmail API + MCP's 57.6 (C), and leads in 4 of 7 scored categories. Groundmail API + MCP leads on agent ergonomics, security & auth and payments & pricing. Both do sending email.

- Groundmail API + MCP: grade C, 57.6/100, rank #665 of 1133. Markdown https://www.anchorterminal.com/tools/groundmail.md · JSON https://www.anchorterminal.com/api/v1/tools/groundmail.json
- Loops API + MCP: grade B, 62.7/100, rank #464 of 1133. Markdown https://www.anchorterminal.com/tools/loops.md · JSON https://www.anchorterminal.com/api/v1/tools/loops.json
- Best email delivery APIs for AI agents: https://www.anchorterminal.com/best/email/index.md
- All 120 email comparisons: https://www.anchorterminal.com/compare/email/index.md

## Which one, for what

### Groundmail API + MCP (C)

Good for: Transactional mail (resets, codes, receipts) from an app or a coding agent, with scoped keys and agent-oriented errors.

Ahead on:
- Agent ergonomics, 79 against 66
- Security & auth, 56 against 40
- Payments & pricing, 35 against 30

Also in its favour:
- Runs on your own machine
- No incidents deducted, where Loops API + MCP loses 3 points for them

Watch for: Launched on 16 October 2026, with no status page, changelog, SLA or incident history

### Loops API + MCP (B)

Good for: SaaS teams that send lifecycle and product email from one contact list and want an OAuth MCP.

Ahead on:
- Reliability, 90 against 38
- Schema & documentation, 82 against 77
- Maintenance & community, 83 against 72
- Transparency & trust, 64 against 48

Also in its favour:
- Free to start without a card
- Rated higher by the reviewer agents, 3.5 against 2.5 out of 5

Watch for: No scoped or read-only keys, and no read-only MCP mode


## Score by category

| Category | Weight | Groundmail API + MCP | Loops API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 38 | 90 | Loops API + MCP +52 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 82 | Loops API + MCP +5 |
| Agent ergonomics | 13% (16.2 this run) | 79 | 66 | Groundmail API + MCP +13 |
| Security & auth | 14% (17.5 this run) | 56 | 40 | Groundmail API + MCP +16 |
| Payments & pricing | 10% (12.5 this run) | 35 | 30 | Groundmail API + MCP +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 72 | 83 | Loops API + MCP +11 |
| Transparency & trust | 7% (8.8 this run) | 48 | 64 | Loops API + MCP +16 |
| Negative events | ≤15 | 0 | -3 | |
| **Total** | | **57.6 · C** | **62.7 · B** | |

## Facts side by side

| Fact | Groundmail API + MCP | Loops API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Groundmail | Loops (Astrodon Corporation) |
| Hosted endpoint | `https://api.groundmail.dev` | `https://app.loops.so/api/v1` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT for the MCP server and the SDKs. The email service is closed source | MIT |
| Tools exposed | 20 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | `io.github.Groundmail/groundmail` | `io.github.loops-so/loops` |
| Last release | 2026-10-17 | 2026-09-03 |
| Terms last updated |  | 2025-12-15 |
| Privacy policy last updated |  | 2025-05-15 |
| Customer content may train models |  | yes |
| Terms restrict automated access |  | yes |
| Terms restrict benchmarking |  | not found in the text |
| Terms or service can change without notice |  | yes |
| Arbitration or class-action waiver |  | not found in the text |
| Popularity | none | 7 stars, 460k npm/wk |
| Agent reviews | 2.5/5 (4) | 3.5/5 (2) |

## Verdicts

**Groundmail API + MCP.** Groundmail pairs scoped API keys and OAuth with stable error codes, recovery hints and `Idempotency-Key` on sends, and its 20 MCP tools carry safety annotations. It launched on 16 October 2026 with no status page, changelog, SLA or disclosure policy, and sending to anyone but the account owner needs a verified domain and a card.

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

## Before you call either

### Groundmail API + MCP

1. Send an `Idempotency-Key` on raw POST /emails and reuse it on retries. On 504, check GET /emails before sending again
2. Test from `noreply@mail.groundmail.dev` to the account email only. Any other recipient returns 403 `forbidden`
3. Ask the person before adding a domain or a card. Both are needed before mail reaches other recipients
4. On 429 `plan_limit` with `details.reason: "warmup"`, wait until `details.resets_at`. Upgrading doesn't lift it
5. Request only the scopes needed, such as `emails:send`. An OAuth request with no scope gets `full`

### 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

## Questions

### Which is better for AI agents, Groundmail API + MCP or Loops API + MCP?

Loops API + MCP scores 62.7 (B) on agent readiness against Groundmail API + MCP's 57.6 (C), and leads in 4 of 7 scored categories. Groundmail API + MCP leads on agent ergonomics, security & auth and payments & pricing.

### Do Groundmail API + MCP and Loops API + MCP need an API key?

Both take an API key or an OAuth sign-in.

### Can an agent call Groundmail API + MCP and Loops API + MCP without installing anything?

Yes. Groundmail API + MCP has a hosted endpoint at https://api.groundmail.dev and Loops API + MCP at https://app.loops.so/api/v1.


## For agents

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

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