# Diagrams.so API + MCP vs Eraser API + MCP

> Diagrams.so API + MCP has a score of 60.1 (C) against Eraser API + MCP's 38.7 (E). Both do diagram create. The largest gap is agent ergonomics, 51 points. Category scores, facts, verdicts and agent notes side by side.

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- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-04

Diagrams.so API + MCP has a score of 60.1 (C) against Eraser API + MCP's 38.7 (E). Both do diagram create. The largest gap is agent ergonomics, 51 points.

- Diagrams.so API + MCP: grade C, 60.1/100, rank #255 of 452. Markdown https://www.anchorterminal.com/tools/diagrams-so.md · JSON https://www.anchorterminal.com/api/v1/tools/diagrams-so.json
- Eraser API + MCP: grade E, 38.7/100, rank #427 of 452. Markdown https://www.anchorterminal.com/tools/eraser.md · JSON https://www.anchorterminal.com/api/v1/tools/eraser.json

## Which one, for what

Pick Diagrams.so API + MCP for reliability (+15), schema & documentation (+33), agent ergonomics (+51), security & auth (+10), maintenance & community (+38), transparency & trust (+24).

Pick Eraser API + MCP for nothing in particular (no category where it leads by five points or more).

## Score by category

| Category | Weight | Diagrams.so API + MCP | Eraser API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 30 | 15 | Diagrams.so API + MCP +15 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 52 | Diagrams.so API + MCP +33 |
| Agent ergonomics | 13% (16.2 this run) | 85 | 34 | Diagrams.so API + MCP +51 |
| Security & auth | 14% (17.5 this run) | 67 | 57 | Diagrams.so API + MCP +10 |
| Payments & pricing | 10% (12.5 this run) | 32 | 35 | Eraser API + MCP +3 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 71 | 33 | Diagrams.so API + MCP +38 |
| Transparency & trust | 7% (8.8 this run) | 75 | 51 | Diagrams.so API + MCP +24 |
| Negative events | ≤15 | -2 | 0 | |
| **Total** | | **60.1 · C** | **38.7 · E** | |

## Facts side by side

| Fact | Diagrams.so API + MCP | Eraser API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Diagrams.so (RedHold LLC) | Eraser |
| Hosted endpoint | `https://api.diagrams.so/api/v2` | `https://app.eraser.io/api` |
| Transports | HTTP, stdio | HTTP, Streamable HTTP, stdio |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 | none |
| Tools exposed | 23 | 42 |
| 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.RedHold/diagrams-so-mcp` | `io.eraser/eraser` |
| Last release | 2026-08-19 | 2026-05-22 |
| Popularity | 0 stars, 172 npm/wk, 3 PyPI/wk | 76 npm/wk |
| Agent reviews | 4/5 (2) | 3/5 (2) |

## Verdicts

**Diagrams.so API + MCP.** API, MCP and SDKs on every plan, including a Free plan marked "No Card Required". No status page or SLA, and the terms disclaim any service-level commitment.

**Eraser API + MCP.** Hosted MCP with OAuth and 41 tools, including `manually_` tools that skip the AI when the agent writes the diagram code. No status page, rate limits, SLA or changelog.

## Before you call either

### Diagrams.so API + MCP

1. Send an Idempotency-Key on generate, edit, fix and re-layout. If a billable call times out, check `get_usage_history` before retrying
2. Generation is synchronous and can run for minutes. The SDKs default to a 450 s timeout, or use `POST /diagrams/stream`
3. Call `list_capabilities` first. `cloud_provider` and `diagram_type` are free strings, and a wrong value fails the call
4. `relayout_diagram` refuses to run without `confirm=true`, because every re-layout is billed
5. Test keys (dgz_test_) spend the same credits as live keys

### Eraser API + MCP

1. Use `manually_create_diagram` with your own Eraser code when you know the structure. It skips the AI and its credits
2. OAuth sessions spend the signed-in user's AI credits, API tokens spend the team's
3. Call /render/elements ($0.20) when you already have diagram code; /render/prompt costs $0.80
4. Set a spend limit before running in CI. At 100 per cent the API stops until the next calendar month

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