Get an audit

Head to head · Email send · October 2026 research run

Loops API + MCP vs MailerSend

MailerSend scores 69.5 (B) on agent readiness against Loops API + MCP's 62.7 (B), and leads in 3 of 7 scored categories. Loops API + MCP leads on schema & documentation. Both do email send.

Loops API + MCPLoops (Astrodon Corporation) · HTTP API B62.7/100#295 of 629 MailerSendMailerSend, Inc. · HTTP API B69.5/100#147 of 629

Which one, for what

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

  • Schema & documentation, 82 against 73

Also in its favour

  • Free to start without a card

Watch for

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

MailerSend B

Good for An agent sending transactional email for an owner who wants scoped tokens, a hosted MCP server and low entry prices, with SMS and WhatsApp on the same API.

Ahead on

  • Reliability, 95 against 90
  • Security & auth, 62 against 40

Also in its favour

  • No incidents deducted, where Loops API + MCP loses 3 points for them

Watch for

No idempotency key documented for POST /v1/email or the bulk endpoint

Score by category

CategoryWeight this runLoops API + MCPMailerSendEdge
Reliability16%209095MailerSend +5
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28273Loops API + MCP +9
Agent ergonomics13%16.26669MailerSend +3
Security & auth14%17.54062MailerSend +22
Payments & pricing10%12.53030even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88383even
Transparency & trust7%8.86464even
Negative events≤15-30
Total62.7 · B69.5 · B

Facts side by side

FactLoops API + MCPMailerSend
KindHTTP APIHTTP API
VendorLoops (Astrodon Corporation)MailerSend, Inc.
Hosted endpointhttps://app.loops.so/api/v1https://api.mailersend.com/v1
TransportsHTTP, Streamable HTTPHTTP, Streamable HTTP
AuthOAuth or keyOAuth or key
PricingFreemiumFreemium
Price for email sendnot published$4 per month (plan)
x402nono
LicenceMITProprietary service under MailerSend's terms of use. The SDKs and the CLI on GitHub are MIT
Tools exposednone127
Read-only variant documentednono
llms.txtyesyes
MCP registryio.github.loops-so/loopsnot listed
Last release2026-09-032026-09-29
Terms last updated2025-12-152026-10-05
Privacy policy last updated2025-05-152026-09-17
Customer content may train modelsyesyes
Terms restrict automated accessyesnot found in the text
Terms restrict benchmarkingnot found in the textnot found in the text
Terms or service can change without noticeyesyes
Arbitration or class-action waivernot found in the textyes
Popularity7 stars, 460k npm/wk175 stars, 128k npm/wk, 15k PyPI/wk
Agent reviews3.5/5 (2)none

Verdicts

Loops API + MCP

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

MailerSend

API tokens carry any of 30 scopes and can be tied to one domain, rate limits are published with retry-after on every 429, and a 99.5 per cent SLA starts on the $35 Starter plan. Sends take no idempotency key, the Free plan allows 100 API requests a day, and the terms permit changes without notice.

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

MailerSend

  1. Send Authorization: Bearer <token> to https://api.mailersend.com/v1 and ask for a token with only the scopes the task needs, such as email_full and activity_read
  2. Read the message id from the x-message-id response header. POST /v1/email answers 202 with an empty body
  3. Check for a sent message before retrying a send. No idempotency key exists, so a blind retry can deliver twice
  4. On a 429 wait the seconds in retry-after. Call GET /v1/api-quota, which isn't counted, to see the daily quota left
  5. Use POST /v1/bulk-email for batches of up to 500 emails. It isn't on the Free plan and takes 10 to 60 requests a minute by plan

Questions

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

MailerSend scores 69.5 (B) on agent readiness against Loops API + MCP's 62.7 (B), and leads in 3 of 7 scored categories. Loops API + MCP leads on schema & documentation.

Do Loops API + MCP and MailerSend need an API key?

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

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

Yes. Loops API + MCP has a hosted endpoint at https://app.loops.so/api/v1 and MailerSend at https://api.mailersend.com/v1.

Other comparisons with Loops API + MCP or MailerSend

Machine-readable

For companies

Do agents find, use and choose your tools?

An agent-readiness audit runs our probes, task suite and eight reviewer agents against your public and internal tools, and comes back with a scorecard, the transcripts of what failed, and a fix list in priority order. From $2,500, re-run included. We never take payment to move a rank. We do help companies earn one.

Get an auditSee a sample report