Loops API + MCP vs MailPace

Loops API + MCP 82

OpenAPI 3.1 in YAML and JSON at app.loops.so, version 1.22.8 on 2 November with 48 paths and 72 operations (25). llms.txt, Markdown copies of every docs page and agent skills for coding agents (10). The reference explains each endpoint. The hosted MCP isn't open source, so we couldn't read its tool definitions (10). Typed inputs in the spec, with ranges such as perPage between 10 and 50 (12). Examples for the API, SDKs and CLI on each examples page, and the spec declares 400, 404, 409, 422 and 429 answers, but the API intro doesn't document the error format (10). Dated API changelog with entries to 20 October, and a versioned spec (15). 25 + 10 + 10 + 12 + 10 + 15 = 82.

MailPace 54

No OpenAPI or other machine-readable contract for the HTTPS API. The MCP server's 12 tools have typed zod inputs and output schemas, but that server isn't published yet, so partial credit (8 of 25). llms.txt answers 404 on mailpace.com and docs.mailpace.com, and no Markdown copies are served (0). The reference states what each endpoint does, and the introduction says when not to use it (transactional only, no batch, no static IPs) (12 of 20). Field tables give type, examples and required or optional, with enums for status, sort and direction and the 50-recipient cap in text (9 of 15). Examples in curl and six languages and a full table of error responses with messages, though several listed messages have a broken quote ({"error:"...) and the send reference says 30 MB where the home page says 25 MB (12 of 15). Version in the path with a promise that an old version runs until a published end-of-life date, and dated changelog posts (13 of 15). Total 54.

Loops API + MCP 90

Statuspage at status.loops.so with components for sending, transactional, API, SMTP relay and webhooks (20). One incident in the 90 days to 2 November, "Delay in email metric processing" on 11 September (about 90 minutes, metrics slow to appear in the app, none lost), which doesn't touch the API or sending, so the record reads as clean (30). 10 requests a second per team, and 60 a minute for the content endpoints (15). 429 with x-ratelimit headers and advice to retry with exponential backoff, and an Idempotency-Key header on event and transactional sends (15). No SLA found on the pricing page (0). GA (10). 20 + 30 + 15 + 15 + 0 + 10 = 90.

MailPace 70

Graded with the hosted lines. A public Upptime status page at status.mailpace.com, driven by the mailpace/status repository, with monitors for the application, SMTP, docs, blog and landing page and GitHub issues as incident reports (20). The 90 days from 8 August hold two incidents, an application outage on 22 September 2026 that the operator put down to an upstream provider returning 5xx (issue open for two minutes), and SMTP down on 2 November 2026 for about 35 minutes, which leaves SMTP at 99.65% for the week. Minor incidents only (20). No rate limit numbers are published; the docs say limits vary by organisation age, plan and history (0). A documented 429 with its message, no Retry-After or backoff guidance, and an Idempotency-Key on sends with written retry rules (10 of 15). The terms guarantee 99% monthly availability of the API and dashboard with a 5% credit per 30 minutes (10). The API is at v1 with no beta label (10). Total 70.

Loops API + MCP 83

API changelog entries on 20 and 6 October, loops-go v0.8.0 and the Loops CLI v0.13.0 on 20 October (30). Since 4 August, seven changelog entries, loops-js 7.2.0 and 7.3.0, loops-go 0.5.0 to 0.8.0, loops-php 3.3.0 and 3.4.0, loops-rb 2.5.0 and nine CLI tags from v0.10.0 to v0.13.1 (20). Public changelog and support. We couldn't see reply times (10). Official SDKs in four languages, current with the spec, and the MCP is listed in the official registry as io.github.loops-so/loops 1.0.0 (13 August) (15). The SDK runs tests in CI on every push (8). 30 + 20 + 10 + 15 + 8 = 83.

MailPace 65

Email Status API documented on 22 October 2026, and the MCP server rewritten as 2.0.0 on 4 November 2026, two days before this check (30). In the 90 days from 8 August, the Q3 changelog post of 31 August, the Email Status docs of 22 October, a mailpace-rails push on 17 October and the MCP rewrite, but only one changelog post (15 of 20). A closed service with email support. Three pull requests to the MCP repository from 2025 have no reply (8 of 15). Not in the official MCP registry (search for mailpace returned nothing on 6 November). The Node library was last pushed in October 2024 and Go in January 2024, while mailpace-rails is current (7 of 15). The MCP server gained CI with tests on 4 November; the older SDKs weren't checked for CI (5 of 10). Total 65.

Loops API + MCP 66

Closed service with published terms and an MIT JavaScript SDK (20). The privacy policy (updated 15 May 2025) says customer contact and message data is returned or deleted within 30 days of termination and account data within 12 months, links a DPA, and says aggregated or anonymised data is used for machine learning in the product (22). Dated deprecations, such as List custom fields on 14 January 2025, but a breaking change on 17 September shipped with same-day notice (12). No subprocessor list. The policy names Stripe, Google Analytics, Segment and GitHub and says data goes to the US (8).

MailPace 75

Closed hosted service under terms that name OhMySMTP Ltd with its company number. The MCP server, SDKs, landing site and status page are MIT (18 of 30). The privacy policy (30 August 2026), the pricing page and the DPA agree on retention, 30 days in the dashboard and 7 more in backups, 37 days at most (25 of 30). The API reference promises an old version runs until a published end-of-life date, and the terms list dated changes. The terms also say changes apply immediately (8 of 20). Sub-processors listed with purpose and location, Freethought hosting in the EU, Hetzner backups in Germany, AppSignal in Amsterdam, Paddle in the UK and Tutanota in Germany (18 of 20). Total 69.

Loops API + MCP 30

No x402, MPP or L402 (0). Paid plans are priced by subscribed contacts on a slider, Growth from $49 a month for up to 5,000 contacts with unlimited sends, re-read on 2 November (10). Free plan of 4,000 sends in any rolling 30 days to 1,000 contacts, with no card (20). Browser signup, no autonomous route (0).

MailPace 25

No x402, MPP or L402 (0). $10 a month for 10,000 emails and $1 per 1,000 after, loaded from Paddle on the pricing page and stated in the comparison pages' tables without login (20). A free plan of up to 100 emails a month is available only by emailing support, so it isn't self-serve (5 of 20). Signup, DKIM verification and payment happen in a browser (0). Total 25.