JustClaw-It vs 21st.dev: which component MCP should your coding agent use?
2026-10-27 · JustClaw-It
Both JustClaw-It and 21st.dev give a coding agent ready-made components over MCP instead of letting it write everything from scratch. They look similar from a distance: free search, paid retrieval, an MCP server and a one-command CLI. Up close they are built for different jobs. This post sets out what each one does well, where each falls short, and how to choose.
Facts about 21st.dev were checked on its own pages on 27 October 2026: pricing, plans, MCP, help centre and terms. Prices and limits change; check them before you buy.
The short answer
- Want polished, designer-made React and Tailwind UI you can preview first? 21st.dev is the better fit. Every component has a live preview and installs through the shadcn CLI.
- Want real code from open-source projects for every layer of the app (auth, payments, webhooks, data access, infrastructure, CLIs, and UI too) in many languages, with the licence of every file you reuse? That is what JustClaw-It is for.
- Many teams will reasonably use both: 21st.dev for the visible interface, JustClaw-It for everything behind it and for UI logic that doesn't need a designer's polish.
What each one is
21st.dev is a community marketplace of more than 12,000 React and Tailwind CSS components, themes and templates. Its MCP server (the 21st MCP, formerly called Magic MCP) lets an agent search the catalogue, pull a component's code and prompt into context, and generate new UI with 21st AI. Components are shown with live previews, ship as a prompt as well as code, and can be installed with npx shadcn@latest add. Setup is npx @21st-dev/cli@latest init --client <client>.
JustClaw-It is a remote MCP server over 1,459,645 components mined from real open-source repositories: functions, classes, handlers and modules. The live category counts include 262,784 UI, 74,256 database, 49,356 auth and 29,307 payments components (a component can carry more than one tag). Each result carries its SPDX licence, copyright holder, source repository, a GitHub permalink and five quality sub-scores. Pulled source starts with an attribution header. The public library only serves permissive and weak-copyleft code. Setup is npx @justclaw-it/cli init.
Side by side
| 21st.dev | JustClaw-It | |
|---|---|---|
| What's in it | 12,000+ React/Tailwind components, themes and templates, made by designers | 1,459,645 components from open-source repositories, many languages |
| Scope | UI | Every layer, UI included; not curated by designers |
| Search | Free | Free (key required, rate-limited) |
| Free tier | Browse and search free; 2 code retrievals or installs a day | 30 pulls on day one, then 10 a day |
| Paid | Builder from $6/month (billed yearly) or $8 (quarterly): unlimited retrieval; AI credits extra | Solo $10, Indie $19, Pro $49 a month; weekly credits, hard cap, no overage |
| Previews | Live, interactive | None; a GitHub permalink to the file |
| Generation | 21st AI generates new components (paid) | None; Pro composes starters from existing components |
| Licence data | Shown on each component page; most components are MIT | SPDX licence, copyright holder and attribution in every API result and in the pulled file |
| Quality signal | Curation and community | Automated scores (five sub-scores and a composite) |
| Security signal | Not listed in its plan comparison | security_advisories warning for repositories named in published CVEs/GHSAs (limited coverage) |
Where 21st.dev is better
- Design quality and visual choice. You can see a component before your agent pulls it. JustClaw-It has no previews; you judge by the code, the score and the repository.
- The UI workflow. Prompts that tell the agent how to rebuild a component in your stack, shadcn installs, themes and templates are a complete front-end toolkit.
- Generation. If nothing in the catalogue fits, 21st AI can make one. JustClaw-It only serves code that already exists.
- Price for heavy UI use. Unlimited retrieval from $6 a month is cheaper than JustClaw-It's metered credits if you pull a lot of UI components.
Where JustClaw-It is better
- Coverage beyond the interface. Stripe webhook verification in Python, JWT middleware in Go, a retry helper in Rust, a Postgres migration script: JustClaw-It indexes all of these, across
c,cpp,csharp,dart,go,java,javascript,kotlin,php,python,ruby,rust,shell,sql,svelte,swift,typescript,vue. Its UI components are plentiful but uncurated: they come from real apps, so quality and style vary more than on a designer marketplace. - Licence and attribution as data, per component. Every search result tells the agent the SPDX licence, whether it is copyleft and who holds the copyright, so the agent can filter (
license: "permissive") before it pulls. The pulled file carries the attribution header. For anyone shipping code to clients, that per-file trail is the point (see why attribution matters). - Real code from real projects. Components come from open-source repositories that people use, not from a showcase, so you see how something is actually done in context.
- Grading and warnings. Five sub-scores and a composite help the agent choose between ten similar results, and a separate
security_advisoriesfield flags repositories named in published advisories. Scores are automated and advisory coverage is limited to a set of well-known repositories, so treat both as signals, not guarantees.
Pricing in practice
Both products follow the same idea: looking is free, taking code is what you pay for.
On the free tiers, 21st.dev gives 2 retrievals a day; JustClaw-It gives 30 pulls on day one and 10 a day after that. On paid plans, 21st.dev's Builder is unlimited for retrieval; JustClaw-It's plans are metered (300 pulls a week on Solo) but hard-capped, so a looping agent cannot run up a bill. If you mostly pull UI and pull a lot, 21st.dev is the cheaper option. If you pull a moderate number of non-UI components and need the licence trail, JustClaw-It is.
Licences: read the fine print on both
21st.dev's help centre says most of its components are MIT and that each component page shows the licence the component carries, and asks you to check it before you ship. Its terms also say that previews, demos and 21st's own changes to a component belong to 21st Labs, separately from the component code. That is reasonable, but it means the licence lives on a web page your agent may never read.
JustClaw-It puts the licence in the tool result and in the file. It still can't make the decision for you: licence data is collected automatically, and you remain responsible for compliance in what you ship.
Using both
Nothing stops an agent from having both servers configured. A sensible split:
- Ask 21st.dev for the pricing table, the hero section and the settings form.
- Ask JustClaw-It for the Stripe webhook handler behind the pricing table, the auth middleware behind the settings form, and the email sender, each with
license: "permissive". - Keep every attribution header, and list the components in
THIRD_PARTY_LICENSES.
Bottom line
21st.dev is the stronger choice for front-end UI: designer-made, previewed and cheap to use heavily. JustClaw-It is the stronger choice for the rest of the codebase and for anyone who needs licence and attribution on every reused file. They overlap less than their landing pages suggest, and they work well together.
Get a free JustClaw-It key (search is free, no card) and try a search from your agent, or read the docs.