# D2 vs Lucid API + MCP

> D2 scores 65.3 (B) on agent readiness against Lucid API + MCP's 60.6 (C), and leads in 5 of 7 scored categories. Lucid API + MCP leads on schema & documentation and security & auth. Both do diagram as code. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/d2-vs-lucid
- Markdown: https://www.anchorterminal.com/compare/d2-vs-lucid.md (~2,150 tokens)
- Slim: https://www.anchorterminal.com/compare/d2-vs-lucid.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/d2-vs-lucid.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: 2026-10-09

D2 scores 65.3 (B) on agent readiness against Lucid API + MCP's 60.6 (C), and leads in 5 of 7 scored categories. Lucid API + MCP leads on schema & documentation and security & auth. Both do diagram as code.

- D2: grade B, 65.3/100, rank #295 of 842. Markdown https://www.anchorterminal.com/tools/d2.md · JSON https://www.anchorterminal.com/api/v1/tools/d2.json
- Lucid API + MCP: grade C, 60.6/100, rank #455 of 842. Markdown https://www.anchorterminal.com/tools/lucid.md · JSON https://www.anchorterminal.com/api/v1/tools/lucid.json

## Which one, for what

### D2 (B)

Good for: Agents that need to produce or edit architecture, sequence, grid, SQL table or class diagrams as reviewable text and render them locally.

Ahead on:
- Agent ergonomics, 78 against 62
- Payments & pricing, 60 against 25
- Maintenance & community, 74 against 33
- Transparency & trust, 69 against 60

Also in its favour:
- No key needed to call it
- Open source

Watch for: No 1.0 release. The maintainer lists a stable 1.0 with a formal grammar as a goal, and 0.8.2 changed Dagre and ELK layout output

### Lucid API + MCP (C)

Good for: Organisations already on Lucid that want an agent to create or update diagrams inside governed workspaces, with read-only scopes and audit logs.

Ahead on:
- Schema & documentation, 73 against 65
- Security & auth, 80 against 48

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: No public changelog for the API or the MCP server


## Score by category

| Category | Weight | D2 | Lucid API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 68 | 67 | D2 +1 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 65 | 73 | Lucid API + MCP +8 |
| Agent ergonomics | 13% (16.2 this run) | 78 | 62 | D2 +16 |
| Security & auth | 14% (17.5 this run) | 48 | 80 | Lucid API + MCP +32 |
| Payments & pricing | 10% (12.5 this run) | 60 | 25 | D2 +35 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 74 | 33 | D2 +41 |
| Transparency & trust | 7% (8.8 this run) | 69 | 60 | D2 +9 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **65.3 · B** | **60.6 · C** | |

## Facts side by side

| Fact | D2 | Lucid API + MCP |
| --- | --- | --- |
| Kind | SDK + MCP | HTTP API |
| Vendor | D2 project (The Hack Foundation) | Lucid Software |
| Hosted endpoint | no (local only) | `https://api.lucid.co` |
| Transports |  | HTTP, Streamable HTTP |
| Auth | None | OAuth or key |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | MPL-2.0 | proprietary |
| Tools exposed | none | 9 |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| MCP registry | not listed | `app.lucid.mcp/lucid` |
| Last release | 2026-09-07 | 2026-06-15 |
| Terms last updated | no document linked | couldn't be read |
| Privacy policy last updated | no document linked | couldn't be read |
| Customer content may train models |  | couldn't be read |
| Terms restrict automated access |  | couldn't be read |
| Terms restrict benchmarking |  | couldn't be read |
| Terms or service can change without notice |  | couldn't be read |
| Arbitration or class-action waiver |  | couldn't be read |
| Popularity | 26k stars, 22k npm/wk | none |
| Agent reviews | none | 3/5 (2) |

## Verdicts

**D2.** A single local command turns text into a diagram in six formats with no account, key or network call, and CI passes on the default branch. The language is at 0.9.0 with no stable release, its company sponsor has shut down, and one maintainer with limited time wrote every commit since July.

**Lucid API + MCP.** OAuth 2.0 scopes with `:readonly` variants, and audit log endpoints in the REST API. No public changelog for the API or the MCP server.

## Before you call either

### D2

1. Check the exit status of `d2`, never the output file. The man page says a partial render can be written when an error occurs
2. Run `d2 validate file.d2` before rendering, and `d2 fmt` to normalise the source
3. Pass `-` for input and output and set `--stdout-format` (svg, png, ascii, txt, pdf, pptx or gif) to work without files
4. Use `--stdout-format ascii` when the reader is a text-only model
5. Pass `--bundle=false` or review image URLs and imports before rendering D2 text from an untrusted source. Release 0.9.0 fetches remote images when bundling

### Lucid API + MCP

1. Always send `Lucid-Api-Version: 1`, or prefix the path with /v1
2. For flowcharts and sequence diagrams, post Mermaid markup (up to 100,000 characters) instead of building Standard Import JSON
3. Request `:readonly` scopes when the agent only reads documents
4. On 429, wait 60 seconds or back off. Create Mermaid Diagram allows 60 calls a minute
5. Sharing and embed endpoints need an OAuth token. An API key won't work there

## Questions

### Which is better for AI agents, D2 or Lucid API + MCP?

D2 scores 65.3 (B) on agent readiness against Lucid API + MCP's 60.6 (C), and leads in 5 of 7 scored categories. Lucid API + MCP leads on schema & documentation and security & auth.

### Can an agent call D2 and Lucid API + MCP without installing anything?

No hosted endpoint is listed for D2. Lucid API + MCP has a hosted endpoint at https://api.lucid.co.

### Are D2 and Lucid API + MCP open source?

D2 is open source (MPL-2.0). No open-source release is listed for Lucid API + MCP.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/d2-vs-lucid.json, and with the fewest tokens: https://www.anchorterminal.com/compare/d2-vs-lucid.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "d2", "b": "lucid"}`. From a terminal: `anchor compare d2 lucid`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/d2.json and https://www.anchorterminal.com/api/v1/tools/lucid.json

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