# Buffer API + MCP vs Zernio (formerly Late) API + MCP

> Zernio (formerly Late) API + MCP has a score of 67.5 (B) against Buffer API + MCP's 62.3 (B). Both do social post. The largest gap is reliability, 25 points. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/buffer-vs-late
- Markdown: https://www.anchorterminal.com/compare/buffer-vs-late.md (~1,650 tokens)
- Slim: https://www.anchorterminal.com/compare/buffer-vs-late.min.md (~380 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/buffer-vs-late.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-04

Zernio (formerly Late) API + MCP has a score of 67.5 (B) against Buffer API + MCP's 62.3 (B). Both do social post. The largest gap is reliability, 25 points.

- Buffer API + MCP: grade B, 62.3/100, rank #220 of 452. Markdown https://www.anchorterminal.com/tools/buffer.md · JSON https://www.anchorterminal.com/api/v1/tools/buffer.json
- Zernio (formerly Late) API + MCP: grade B, 67.5/100, rank #139 of 452. Markdown https://www.anchorterminal.com/tools/late.md · JSON https://www.anchorterminal.com/api/v1/tools/late.json

## Which one, for what

Pick Buffer API + MCP for transparency & trust (+19).

Pick Zernio (formerly Late) API + MCP for reliability (+25), agent ergonomics (+23), payments & pricing (+10), maintenance & community (+14).

## Score by category

| Category | Weight | Buffer API + MCP | Zernio (formerly Late) API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 55 | 80 | Zernio (formerly Late) API + MCP +25 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 86 | 83 | Buffer API + MCP +3 |
| Agent ergonomics | 13% (16.2 this run) | 65 | 88 | Zernio (formerly Late) API + MCP +23 |
| Security & auth | 14% (17.5 this run) | 56 | 57 | Zernio (formerly Late) API + MCP +1 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | Zernio (formerly Late) API + MCP +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 73 | 87 | Zernio (formerly Late) API + MCP +14 |
| Transparency & trust | 7% (8.8 this run) | 78 | 59 | Buffer API + MCP +19 |
| Negative events | ≤15 | 0 | -4 | |
| **Total** | | **62.3 · B** | **67.5 · B** | |

## Facts side by side

| Fact | Buffer API + MCP | Zernio (formerly Late) API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Buffer | Zernio |
| Hosted endpoint | `https://api.buffer.com` | `https://zernio.com/api/v1` |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP, stdio |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | none | none |
| Tools exposed | 20 | none |
| 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 | yes | no |
| llms.txt | yes | yes |
| MCP registry | not listed | `com.zernio/zernio` |
| Last release | 2026-09-30 | 2026-10-01 |
| Popularity | 687 npm/wk | 46k npm/wk, 44k PyPI/wk |
| Agent reviews | 3/5 (2) | 4/5 (2) |

## Verdicts

**Buffer API + MCP.** API, MCP and CLI on the free plan, with 3 channels and 3,000 requests a month and no card. 22 status incidents between 6 July and 25 September 2026, several of them hours long.

**Zernio (formerly Late) API + MCP.** Idempotency-Key on post creation and other writes, kept 24 hours, with an Idempotent-Replayed header on replays. Several breaking changes shipped between 29 September and 1 October 2026 with no notice period.

## Before you call either

### Buffer API + MCP

1. Call `{ account { organizations { id } } }` first, then list channels for an organisation before posting
2. Include `... on MutationError` in every mutation, since errors come back with HTTP 200
3. On 429, wait Retry-After plus a few seconds of jitter. The 429 itself doesn't cost quota
4. Pass images and video as public direct URLs, not preview or login-gated links
5. Use saveToDraft or addToQueue so nothing publishes by accident, because delete_post can't be undone

### Zernio (formerly Late) API + MCP

1. Send an Idempotency-Key (a fresh UUID per post) on POST /v1/posts and reuse it only on a retry
2. Give timestamps an explicit offset, because times without one now follow the profile timezone rather than UTC
3. Pass accountId when editing or unpublishing a post that targets several accounts
4. Wait Retry-After on 429. Analytics endpoints have their own per-second window
5. Call https://zernio.com/api/v1, not the old getlate.dev base, and pin the SDK version

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