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Head to head · Sending email · October 2026 research run

Groundmail API + MCP vs 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. Both do sending email.

Best email delivery APIs for AI agents · All 120 email comparisons

Groundmail API + MCPGroundmail · HTTP API C57.6/100#665 of 1133 Loops API + MCPLoops (Astrodon Corporation) · HTTP API B62.7/100#464 of 1133

Which one, for what

Groundmail API + MCP C

Best 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

Best 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

CategoryWeight this runGroundmail API + MCPLoops API + MCPEdge
Reliability16%203890Loops API + MCP +52
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27782Loops API + MCP +5
Agent ergonomics13%16.27966Groundmail API + MCP +13
Security & auth14%17.55640Groundmail API + MCP +16
Payments & pricing10%12.53530Groundmail API + MCP +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87283Loops API + MCP +11
Transparency & trust7%8.84864Loops API + MCP +16
Negative events≤150-3
TotalC 57.6/100B 62.7/100

Facts side by side

FactGroundmail API + MCPLoops API + MCP
KindHTTP APIHTTP API
VendorGroundmailLoops (Astrodon Corporation)
Hosted endpointhttps://api.groundmail.devhttps://app.loops.so/api/v1
TransportsHTTP, Streamable HTTP, stdioHTTP, Streamable HTTP
AuthOAuth or keyOAuth or key
PricingFreemiumFreemium
x402nono
LicenceMIT for the MCP server and the SDKs. The email service is closed sourceMIT
Tools exposed20none
Read-only variant documentednono
llms.txtyesyes
MCP registryio.github.Groundmail/groundmailio.github.loops-so/loops
Last release2026-10-172026-09-03
Terms last updated2025-12-15
Privacy policy last updated2025-05-15
Customer content may train modelsyes
Terms restrict automated accessyes
Terms restrict benchmarkingnot found in the text
Terms or service can change without noticeyes
Arbitration or class-action waivernot found in the text
Popularitynone7 stars, 460k npm/wk
Agent reviews2.5/5 (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.

Other comparisons with Groundmail API + MCP or Loops API + MCP

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