# Mailchimp Marketing API (slim)

> Intuit Mailchimp's Marketing API manages audiences, contacts, tags, segments, events, campaigns, automations and reports for a Mailchimp account. It is a REST API at https://api.mailchimp.com/3.0/ that takes an API key or an OAuth 2 token.

- Full: https://www.anchorterminal.com/tools/mailchimp-marketing.md (~10,100 tokens) · this version ~2,280 tokens · JSON https://www.anchorterminal.com/tools/mailchimp-marketing.json · canonical https://www.anchorterminal.com/tools/mailchimp-marketing
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-09

**C · 57.4/100 · rank #549 of 842 · #4 in Lifecycle marketing & customer engagement · not agent-ready · confidence medium**


Assessment: A public OpenAPI 3.1 file covers all 297 operations, every docs page has a Markdown copy, and responses can be trimmed with `fields`. An API key carries full account access with no read-only option. The quick start's TypeScript package was not on npm on 8 October 2026, and the changelog's newest entry is 19 August 2025.

## Facts

- Kind: HTTP API · vendor: Intuit Mailchimp · category: Lifecycle marketing & customer engagement · legal entity: The Rocket Science Group LLC d/b/a Mailchimp · provenance 92/100
- Endpoint: `https://api.mailchimp.com/3.0` (HTTP)
- Auth: OAuth or key · pricing: Freemium · x402: no · licence: Proprietary service under Mailchimp's Standard Terms of Use and API Use Policy. The generated client libraries declare Apache-2.0 in their package metadata
- Probe metrics: not measured yet (probes haven't run)
- API: REST over HTTPS at https://api.mailchimp.com/3.0/, JSON bodies, 297 operations (151 GET, 73 POST, 35 DELETE, 32 PATCH, 6 PUT). Actions that are not CRUD sit under `actions/`. TLS 1.2 or higher
- OpenAPI: OpenAPI 3.1.1 at https://api.mailchimp.com/schema/openapi/OpenAPI.json?expand (about 17 MB expanded, version label 0.1.0-dev). A 1.2 MB OpenAPI 3.1.0 copy at https://mailchimp.com/developer/openapi/api-reference.json has the same 297 operations without error responses or examples
- Credentials: API keys with full account access, named, several per account, revocable, bounded by the creator's user level. New keys expire after one year from 22 June 2026 per the help centre. OAuth 2 authorisation code grant with no scopes and tokens that do not expire
- Limits: 10 simultaneous connections per user, 120-second timeout per call, `count` up to 1,000, 500 pending batch requests and 500 pending batch webhook events. No per-minute figure is published
- Errors: `application/problem+json` with `type`, `title`, `status`, `detail`, `instance` and a per-field `errors` list on validation failures. 429 for too many connections. The `X-Trigger-Error` header returns a named error on demand
- Sizing responses: `fields` and `exclude_fields` with dot notation on 130 operations, `count` and `offset` on 59. No cursor pagination
- Batch: POST `/batches` runs many operations in the background and returns a gzipped archive of results. Up to 20 batch webhooks
- Sending: `actions/send`, `actions/schedule`, `actions/unschedule`, `actions/test` and `actions/cancel-send` on campaigns, a `send-checklist` read, and the same send and schedule actions for SMS campaigns
- Events and flows: POST `/lists/{list_id}/members/{subscriber_hash}/events` records a named event, with `is_syncing` to skip automations. POST `/customer-journeys/journeys/{journey_id}/steps/{step_id}/actions/trigger` starts a flow step built in the app. Flows are not created by API
- Webhooks: Audience webhooks with optional HMAC-SHA256 signing in `X-Mailchimp-Signature`, a five-minute timestamp window, and up to 20 retries at 15 to 25 minute intervals before the webhook is disabled
- Client libraries: Nine Fern-generated libraries on GitHub since 9 September 2026, release 1.0.3 of TypeScript, Python and Go on 5 October 2026. Rust 0.0.221 and Ruby 0.0.218 are on their registries. The TypeScript package was not on npm, and PyPI held the 2022 library 3.0.80, on 8 October 2026
- CLI: `mcapi`, written in Rust, one subcommand per endpoint, key in `MCAPI_TOKEN`, releases 0.0.212 and 0.0.213 on 18 September 2026
- Agent tools: A docs-search MCP server with one read-only tool, llms.txt at each level of the docs, and four agent skills (`set-consent-correctly`, `set-up-oauth`, `subscribe-to-webhooks`, `run-bulk-jobs`) installed with `npx skills add https://mailchimp.com/developer`
- Plans: Free 250 contacts and 500 sends a month. Essentials up to 50,000 contacts with sends at 10 times the contact limit. Standard up to 100,000 with 12 times. Premium by quote above 250,000. What the API can do depends on the plan
- Certifications: SOC 2 reports and ISO 27001 per mailchimp.com/about/security, with reports in the Intuit compliance portal. A responsible disclosure programme with no rewards
- Status: status.mailchimp.com with Admin and API components for data centres US1 to US21 and event history by month
- Prices: Essentials plan, up to 500 contacts $13 per month (plan); Standard plan, up to 500 contacts $20 per month (plan); Premium plan, starting price $350 per month (plan)

- Scores: Reliability 60, Performance pending, Schema & documentation 76, Agent ergonomics 73, Security & auth 46, Payments & pricing 25, Task success pending, Maintenance & community 63, Transparency & trust 74 · negative events -2 · total over the 7 assessed categories
- Why: Reliability, Graded on the hosted REST API with the hosted lines. · Schema & documentation, An OpenAPI 3.1.1 file with all 297 operations is public on the API host, and the docs site serves a 1.2 MB copy (25). · Agent ergonomics, Graded on the API, since the MCP server only searches docs. · Security & auth, API keys are named, several to an account, revocable, and bounded by the creating user's level. · Payments & pricing, No x402, MPP or L402 (0). · Maintenance & community, Release 1.0.3 of the TypeScript, Python and Go client libraries is dated 5 October 2026, three days before this check (30). · Transparency & trust, Closed service with published terms, an API Use Policy and a named contracting entity.
- Sources: 45, open questions: 14, both in the full twin
- Capabilities: marketing.profiles, marketing.events, marketing.segments, marketing.campaigns, marketing.journeys, email.templates
- JSON: https://www.anchorterminal.com/api/v1/tools/mailchimp-marketing.json
- Verify (for the vendor): the badge `https://www.anchorterminal.com/badges/mailchimp-marketing.svg` or a link to https://www.anchorterminal.com/tools/mailchimp-marketing from a page on mailchimp.com or one of its subdomains, or the README of github.com/mailchimp/mailchimp-marketing-typescript-sdk, then `POST https://www.anchorterminal.com/api/v1/verify` `{"slug", "url"}` or `verify_listing` at /mcp; re-checked weekly, no effect on the grade. Snippets in the full twin.

## Before you call it

1. Send the key or OAuth token as `Authorization: Bearer` to `https://api.mailchimp.com/3.0/`. Treat it as full account access and keep it server-side
2. Address a contact by the MD5 hash of the lowercase email address, and use PUT on `/lists/{list_id}/members/{subscriber_hash}` so a retry does not create a duplicate
3. Ask a person before POST `/campaigns/{campaign_id}/actions/send`. Read `/campaigns/{campaign_id}/send-checklist` and use `actions/test` first
4. Keep to 10 concurrent requests per user, and send large jobs to `/batches`. A 429 names no wait time, so back off and retry
5. Add `fields=` to every list call and set `count` (default 10, maximum 1,000) with `offset`
6. Set `is_syncing` to true when loading historical events so they do not trigger automations

## Connect

```bash
curl -sS \
  "https://api.mailchimp.com/3.0/ping" \
  --user "anystring:${apikey}"
```

```bash
claude mcp add --transport http fern_mcp_mailchimp-docs \
  https://mailchimp.com/developer/_mcp/server
```
Full config and headless snippets are in the full page. Through letme (picks today, calling later): https://letme.dev/mailchimp-marketing

## Similar tools

| Tool | Grade | Score | Shared capabilities | Slim |
| --- | --- | --- | --- | --- |
| Customer.io | BB | 74.5 | marketing.profiles, marketing.events, marketing.segments, marketing.campaigns, marketing.journeys, email.templates | https://www.anchorterminal.com/tools/customer-io.min.md |
| Klaviyo API + MCP | BB | 71.7 | marketing.profiles, marketing.events, marketing.segments, marketing.campaigns, marketing.journeys, email.templates | https://www.anchorterminal.com/tools/klaviyo.min.md |
| Iterable | C | 55.2 | marketing.profiles, marketing.events, marketing.segments, marketing.campaigns, marketing.journeys, email.templates | https://www.anchorterminal.com/tools/iterable.min.md |
| Braze | C | 61.2 | marketing.profiles, marketing.events, marketing.campaigns, marketing.journeys, marketing.segments | https://www.anchorterminal.com/tools/braze.min.md |
| ActiveCampaign | D | 50.5 | marketing.profiles, marketing.events, marketing.segments, marketing.campaigns, marketing.journeys | https://www.anchorterminal.com/tools/activecampaign.min.md |


## Panel reviews (0, desk reviews from public material, no calls made)