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Head to head · Design canvases · October 2026 research run

Melius vs Subframe

Melius scores 54.1 (C) on agent readiness against Subframe's 39.7 (E), and leads in 4 of 7 scored categories. Subframe leads on payments & pricing. Both do design canvases.

Best design workspace and canvas APIs for AI agents · All 49 design comparisons

MeliusMelius AI, Inc. · HTTP API C54.1/100#695 of 950 SubframeAtomic Design Inc · MCP server E39.7/100#915 of 950

Which one, for what

Melius C

Good for An agent producing batches of ad creative, product images or short videos on a shared canvas that people then review, with many models behind one key.

Ahead on

  • Reliability, 69 against 19
  • Schema & documentation, 70 against 54

Also in its favour

  • No incidents deducted, where Subframe loses 3 points for them

Watch for

API keys have no scopes. A key works with its creator's role in every team the creator belongs to

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

  • Payments & pricing, 33 against 20

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

CategoryWeight this runMeliusSubframeEdge
Reliability16%206919Melius +50
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27054Melius +16
Agent ergonomics13%16.25147Melius +4
Security & auth14%17.54344Subframe +1
Payments & pricing10%12.52033Subframe +13
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86665Melius +1
Transparency & trust7%8.85557Subframe +2
Negative events≤150-3
Total54.1 · C39.7 · E

Facts side by side

FactMeliusSubframe
KindHTTP APIMCP server
VendorMelius AI, Inc.Atomic Design Inc
Hosted endpointhttps://api.melius.com/api/v1https://mcp.subframe.com/mcp
TransportsHTTP, Streamable HTTPHTTP
AuthOAuth or keyOAuth or key
PricingFreemiumFreemium
x402nono
LicenceProprietary service under Melius's terms of service. The mel CLI on npm is MIT, with no public source repository foundProprietary 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 exposed7546
Read-only variant documentednoyes
llms.txtyesyes
Last release2026-09-102026-10-08
Terms last updatedno date given2026-01-22
Privacy policy last updatedno date given2026-01-22
Customer content may train modelsnot found in the textnot found in the text
Terms restrict automated accessyesnot found in the text
Terms restrict benchmarkingyesnot found in the text
Terms or service can change without noticeyesnot found in the text
Arbitration or class-action waiveryesnot found in the text
Popularity9 npm/wk435 stars, 1k npm/wk

Verdicts

Melius

One backend serves a 59-operation REST API with a public OpenAPI spec, a hosted MCP server with OAuth sign-in and a JSON-only CLI, and the status page shows no incidents since July 2026. API keys carry no scopes and work with their creator's role, and no rate-limit numbers, changelog or per-model credit prices are published.

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

Melius

  1. Generate by creating a node on a canvas, starting a run with POST /nodes/{nodeId}/runs, then polling GET /node-runs/{nodeRunId} until status is finished or failed
  2. Over MCP, call get_guide first, show_presence before node changes and canvas_plan_layout before bulk_create_nodes
  3. On 429 wait Retry-After seconds. After a timeout or 5xx on a write, read the canvas or run state before resubmitting, because there are no idempotency keys
  4. Read credit costs from GET /generation/models?category=image before a bulk run. A 400 can mean the team is out of credits
  5. Downloads arrive as a ZIP from a signed URL. Fetch that URL without the Authorization header

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, Melius or Subframe?

Melius scores 54.1 (C) on agent readiness against Subframe's 39.7 (E), and leads in 4 of 7 scored categories. Subframe leads on payments & pricing.

Do Melius and Subframe need an API key?

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

Can an agent call Melius and Subframe without installing anything?

Yes. Melius has a hosted endpoint at https://api.melius.com/api/v1 and Subframe at https://mcp.subframe.com/mcp.

Other comparisons with Melius or Subframe

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