# pen.dev vs Subframe

> pen.dev scores 47.6 (D) to Subframe's 39.7 (E) for design files. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/pen-dev-vs-subframe
- Markdown: https://www.anchorterminal.com/compare/pen-dev-vs-subframe.md (~2,300 tokens)
- Slim: https://www.anchorterminal.com/compare/pen-dev-vs-subframe.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/pen-dev-vs-subframe.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

pen.dev scores 47.6 (D) on agent readiness against Subframe's 39.7 (E), and leads in 4 of 7 scored categories. Subframe leads on security & auth and maintenance & community. Both do design files.

- pen.dev: grade D, 47.6/100, rank #832 of 950. Markdown https://www.anchorterminal.com/tools/pen-dev.md · JSON https://www.anchorterminal.com/api/v1/tools/pen-dev.json
- Subframe: grade E, 39.7/100, rank #915 of 950. Markdown https://www.anchorterminal.com/tools/subframe.md · JSON https://www.anchorterminal.com/api/v1/tools/subframe.json
- Best design workspace and canvas APIs for AI agents: https://www.anchorterminal.com/best/design/index.md
- All 49 design comparisons: https://www.anchorterminal.com/compare/design/index.md

## Which one, for what

### pen.dev (D)

Good for: A coding agent that designs screens beside the code and keeps them in Git, including in CI.

Ahead on:
- Reliability, 33 against 19
- Schema & documentation, 61 against 54
- Agent ergonomics, 66 against 47
- Payments & pricing, 38 against 33

Also in its favour:
- Runs on your own machine
- No incidents deducted, where Subframe loses 3 points for them

Watch for: No changelog. The three desktop releases on GitHub have empty notes, and the format docs reserve the right to make breaking changes

### Subframe (E)

Good for: A coding agent working beside a team that designs React and Tailwind interfaces in Subframe and wants the design as code, with a read-only route for review.

Ahead on:
- Security & auth, 44 against 33
- Maintenance & community, 65 against 59

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

Watch for: 46 tools are documented with no toolsets, and the vendor's `design` skill that explains them is about 55 KB of text


## Score by category

| Category | Weight | pen.dev | Subframe | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 33 | 19 | pen.dev +14 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 61 | 54 | pen.dev +7 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 47 | pen.dev +19 |
| Security & auth | 14% (17.5 this run) | 33 | 44 | Subframe +11 |
| Payments & pricing | 10% (12.5 this run) | 38 | 33 | pen.dev +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 59 | 65 | Subframe +6 |
| Transparency & trust | 7% (8.8 this run) | 53 | 57 | Subframe +4 |
| Negative events | ≤15 | 0 | -3 | |
| **Total** | | **47.6 · D** | **39.7 · E** | |

## Facts side by side

| Fact | pen.dev | Subframe |
| --- | --- | --- |
| Kind | MCP server | MCP server |
| Vendor | High Agency, Inc. | Atomic Design Inc |
| Hosted endpoint | no (local only) | `https://mcp.subframe.com/mcp` |
| Transports | stdio | HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Proprietary. The CLI package on npm carries a proprietary licence file, and the apps fall under the vendor's EULA | Proprietary service under Atomic Design's terms of service. `@subframe/cli` and `@subframe/core` are marked ISC in their package files and the Claude Code plugin MIT in its manifest, with no licence file in the repository |
| Tools exposed | 6 | 46 |
| Read-only variant documented | no | yes |
| llms.txt | no | yes |
| Last release | 2026-10-08 | 2026-10-08 |
| Terms last updated | 2026-10-06 | 2026-01-22 |
| Privacy policy last updated | 2026-10-06 | 2026-01-22 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | yes | not found in the text |
| Terms restrict benchmarking | yes | not found in the text |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 3.5k npm/wk | 435 stars, 1k npm/wk |

## Verdicts

**pen.dev.** An agent can create, edit and export `.pen` designs without a GUI through the `pen` CLI, with four compact MCP tools that carry annotations and a documented JSON format. The software is closed and needs a pen.dev account. No changelog, status page or security contact was found, and 14 public issue reports had no reply on 8 October 2026.

**Subframe.** An agent can read and change pages, components, snippets and themes in a Subframe project through a hosted MCP server with OAuth, and Viewer accounts get a read-only server. The server lists 46 tools, and no status page, rate limits, changelog or security contact were found. Three tools were renamed in September 2026 with no notice found.

## Before you call either

### pen.dev

1. Call `read_skill()`, then `read_skill({ path: "pen-schema.md" })` and `read_skill({ path: "execute.md" })` before the first `execute`. The tool description alone doesn't document the operations
2. Call `get_app_state()` and confirm the active document before editing. The MCP server works on whichever `.pen` file is open in the app
3. In headless `pen interactive`, call `save()` before `exit()`, and keep `--in` and `--out` on different paths to preserve the source
4. Check that an export file exists. The docs say an export failure can print an error without a nonzero exit status
5. In CI set `PEN_CLI_KEY` plus a provider key such as `ANTHROPIC_API_KEY`. Run `pen version`, since `pen --version` is not a flag

### Subframe

1. Connect with an MCP client that supports OAuth. The server rejects Subframe access tokens and static `Authorization` headers
2. Pass `projectId` on every call. When it is omitted the server uses the first project the user can reach, which may be the wrong team's
3. After `design_page`, `design_component` or `edit_component`, call `wait_for_jobs` with the `jobId` before reading the result. Earlier reads return stale content
4. Ask the owner before any delete tool or a theme token deletion. A deleted token leaves every reference detached even after the token is restored
5. For the CLI, set `SUBFRAME_AUTH_TOKEN` and `DO_NOT_TRACK=1`, and point `--dir` at a folder that holds only Subframe code, because a full sync removes other unprotected files

## Questions

### Which is better for AI agents, pen.dev or Subframe?

pen.dev scores 47.6 (D) on agent readiness against Subframe's 39.7 (E), and leads in 4 of 7 scored categories. Subframe leads on security & auth and maintenance & community.

### Do pen.dev and Subframe need an API key?

Both take an API key or an OAuth sign-in.

### Can an agent call pen.dev and Subframe without installing anything?

pen.dev runs on your own machine, with no hosted endpoint listed. Subframe has a hosted endpoint at https://mcp.subframe.com/mcp.


## For agents

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

## Other comparisons with pen.dev or Subframe

- [Figma API + MCP vs pen.dev](https://www.anchorterminal.com/compare/figma-mcp-vs-pen-dev.md)
- [Figma API + MCP vs Subframe](https://www.anchorterminal.com/compare/figma-mcp-vs-subframe.md)
- [Framer Server API vs pen.dev](https://www.anchorterminal.com/compare/framer-vs-pen-dev.md)
- [Framer Server API vs Subframe](https://www.anchorterminal.com/compare/framer-vs-subframe.md)
- [Miro API + MCP vs pen.dev](https://www.anchorterminal.com/compare/miro-vs-pen-dev.md)
- [Miro API + MCP vs Subframe](https://www.anchorterminal.com/compare/miro-vs-subframe.md)
- [pen.dev vs Penpot API + MCP](https://www.anchorterminal.com/compare/pen-dev-vs-penpot.md)
- [pen.dev vs Sketch](https://www.anchorterminal.com/compare/pen-dev-vs-sketch.md)
- [pen.dev vs Zeplin](https://www.anchorterminal.com/compare/pen-dev-vs-zeplin.md)
- [Penpot API + MCP vs Subframe](https://www.anchorterminal.com/compare/penpot-vs-subframe.md)
- [Sketch vs Subframe](https://www.anchorterminal.com/compare/sketch-vs-subframe.md)
- [Subframe vs Zeplin](https://www.anchorterminal.com/compare/subframe-vs-zeplin.md)
- [Melius vs pen.dev](https://www.anchorterminal.com/compare/melius-vs-pen-dev.md)
- [Melius vs Subframe](https://www.anchorterminal.com/compare/melius-vs-subframe.md)