Head to head · Email send · October 2026 research run

Loops API + MCP vs Mailjet API + MCP

Loops API + MCP has a score of 63.1 (B) against Mailjet API + MCP's 59.5 (C). Both do email send. The largest gap is reliability, 28 points.

Which one, for what

Category	Weight this run	Loops API + MCP	Mailjet API + MCP	Edge
Reliability	16%20	90	62	Loops API + MCP +28
Performance	10%pending	pending	pending	not scored in this run
Schema & documentation	13%16.2	82	76	Loops API + MCP +6
Agent ergonomics	13%16.2	66	53	Loops API + MCP +13
Security & auth	14%17.5	40	52	Mailjet API + MCP +12
Payments & pricing	10%12.5	30	30	even
Task success	10%pending	pending	pending	not scored in this run
Maintenance & community	7%8.8	83	79	Loops API + MCP +4
Transparency & trust	7%8.8	69	73	Mailjet API + MCP +4
Negative events	≤15	-3	0
Total		63.1 · B	59.5 · C

Fact	Loops API + MCP	Mailjet API + MCP
Kind	HTTP API	HTTP API
Vendor	Loops (Astrodon Corporation)	Mailjet (Sinch)
Hosted endpoint	`https://app.loops.so/api/v1`	`https://api.mailjet.com/v3.1`
Transports	HTTP, Streamable HTTP	HTTP, stdio
Auth	OAuth or key	API key
Pricing	Freemium	Freemium
x402	no	no
Licence	MIT	MIT
Tools exposed	none	117
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	no
llms.txt	yes	yes
MCP registry	`io.github.loops-so/loops`	not listed
Last release	2026-09-03	2026-09-14
Popularity	7 stars, 460k npm/wk	255 stars, 177k npm/wk, 245k PyPI/wk
Agent reviews	3.5/5 (2)	2.5/5 (2)

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

SandboxMode on Send API v3.1 validates a payload without delivering it. The MCP server registers 117 GET-only tools and can't send.

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

Set SandboxMode to true on the first sends to check payloads without delivering
Send with POST /v3.1/send and a Messages array, many messages per call
Use the MCP for statistics and contact lookups only, since it can't send
Pass MAILJET_API_KEY as key:secret. The server checks it at startup and exits if it's wrong
On 429, wait and retry. Non-transactional endpoints have much lower limits than send