AtCoder MCP Server
What it does
Search AtCoder problems and fetch public problem statements through MCP.
- Connects Runs in the cloud
- Account or key No key needed
- Category Search & AI memory
Install
Pick the AI app you use, then copy the settings.
Passed 5/5 checks · What you ask goes through the maker’s server (api.ksrnyx.top) · ✓ Commands checked Nov 13, 2026
First: which AI do you use?
Pick your app and the steps appear below.
Works with Claude · about 2 min
No key, nothing to install · Set it up once on claude.ai or the desktop app, then use it in chat · free accounts can add 1 · on Team/Enterprise an Owner adds it
Open Claude’s Connectors page
CustomizeConnectors
Click “Add” → “Custom” → “Web” and fill in these 2 fields
Copy each value into the field with the same name in Claude, then click Continue
Name · NameAtCoder MCP ServerRemote MCP server URL · Addresshttps://api.ksrnyx.top/oj-mcp/atcoder/mcpClick Continue past the sign-in settings Claude detected · under Authentication choose what the maker says (Sign in now, Sign in when needed or No sign in), then click Add
Turn it on in a chat
+ConnectorsAtCoder MCP Server
Try it
Use AtCoder MCP Server and tell me what you can do for me, then show me one thing✓ If Claude says it is using AtCoder MCP Server or shows a AtCoder MCP Server tool in the answer, you are connected
Menu names checked against Anthropic’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Works with ChatGPT, depending on your plan
Full MCP: ChatGPT Business, Enterprise or Edu on the web · Pro: connects with read/fetch permissions, so tools that change data may not work · Plus: not confirmed in OpenAI’s docs; if you see an add-custom-MCP option on the Plugins page you can try these steps · web only
Open ChatGPT’s add-MCP page on the web
Plugins+Add custom MCP server
Fill in the name and address
Enter a name, paste the address under Connection, tick the risk warning and click Create as a plugin
Name · NameAtCoder MCP ServerConnection · Addresshttps://api.ksrnyx.top/oj-mcp/atcoder/mcpPick AtCoder MCP Server in a chat
Start a new chat and pick AtCoder MCP Server from your plugins before typing
Try it
Use AtCoder MCP Server and tell me what you can do for me, then show me one thing✓ If ChatGPT says it is using AtCoder MCP Server or shows a AtCoder MCP Server tool in the answer, you are connected
Menu names checked against OpenAI’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Works with Claude Code · about 2 min
No key, nothing to install
Open Terminal
Mac: press Command+Space and type Terminal · Windows: open PowerShell
Paste this command and press Enter
claude mcp add --transport http --scope user atcoder https://api.ksrnyx.top/oj-mcp/atcoder/mcpType /mcp in Claude Code
You should see AtCoder MCP Server listed as connected
Try it
Use AtCoder MCP Server and tell me what you can do for me, then show me one thing✓ If Claude Code says it is using AtCoder MCP Server or shows a AtCoder MCP Server tool in the answer, you are connected
Menu names checked against Anthropic’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Works with Cursor · about 2 min
No key, nothing to install
Open the AI chat in Cursor in Agent mode
Try it
Use AtCoder MCP Server and tell me what you can do for me, then show me one thing✓ If Cursor says it is using AtCoder MCP Server or shows a AtCoder MCP Server tool in the answer, you are connected
Menu names checked against Cursor’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Works with VS Code · about 2 min
No key, nothing to install
Open the AI chat in VS Code in Agent mode
Try it
Use AtCoder MCP Server and tell me what you can do for me, then show me one thing✓ If VS Code says it is using AtCoder MCP Server or shows a AtCoder MCP Server tool in the answer, you are connected
Menu names checked against VS Code’s help page on Nov 11, 2026 · your screen may differ slightly by app version
Other apps that use MCP, such as Windsurf, Zed or Gemini CLI, each add servers differently. See how in the app list.
Address for apps that connect over the web
https://api.ksrnyx.top/oj-mcp/atcoder/mcpJSON settings are under “For developers” below
For developers: Terminal commands and JSON settings
Over the web
Claude Code
claude mcp add --transport http --scope user atcoder https://api.ksrnyx.top/oj-mcp/atcoder/mcpCursor (~/.cursor/mcp.json)
{
"mcpServers": {
"atcoder": {
"url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"
}
}
}VS Code (mcp.json)
{
"servers": {
"atcoder": {
"type": "http",
"url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"
}
}
}These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.
At a glance
Which apps can use it
Based on how this server connects and on each app’s own docs, checked Nov 10, 2026.
Connect over the internet in
ClaudeChatGPTGooseLM StudioMsty StudioCherry StudioCursorVS Code + GitHub CopilotVisual StudioWindsurf (Devin Desktop)ZedKiroClineContinueJetBrains AI AssistantClaude CodeCodex CLIGemini CLIOpenCodenodecodeWarpLibreChatOpen WebUIRaycast
Related guides
What it can do
Tool names and descriptions exactly as the server reported them on Nov 11, 2026. The maker wrote them, not us; we show them as plain text.
oj_capabilitiesReport the audited anonymous AtCoder read surface and explicitly unsupported operations.
oj_healthReport local readiness and the latest observed AtCoder page-read status without probing upstream.
oj_fetch_problemFetch one public problem statement from an exact contest/task pair or canonical atcoder.jp task URL. Returns sanitized HTML with preserved math, samples, limits, hashes, and source provenance.
oj_search_problemsResolve exactly one contest/task id, atcoder:contest/task id, or canonical task URL. Free-text and catalog crawling are not supported.
Basic checksi
We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 16, 2026
- ✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account ketherworks, which owns the repo
- ✓ Pass
Still maintained
Code last changed 2 months ago
- ✓ Pass
Has a licence
Uses MIT
- ✓ Pass
- – Not applicable
Sign-in with OAuth
No sign-in needed
- ✓ Pass
No hidden instructions in tool descriptions
Read 4 tool descriptions and found no hidden instructions to the AI
Makers: ask for a re-check or report wrong info
Discussion
Ask, share a tip or report that it does not work. Sorted by what people marked helpful.
No posts yet. Be the first to ask or share.
Posts here are written by users, not the PopNx team.
User reviews
No reviews yet
Compared with others in Search & AI memoryi
- More stars than 0% of the other 6194 servers in this category
- Published to the registry more recently than 22% of the other 6194 servers in this category
- Basic checks equal to or better than 100% of the other 6194 servers in this category
Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.
Common questions
Is AtCoder MCP Server safe?
It passed 5 of 5 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.
What keys or codes does it need?
The registry does not list a required key, though some servers ask you to sign in on first use.
Does it run on my computer or in the cloud?
It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.
Is it still maintained?
The GitHub repo last changed 2 months ago, and the latest version (0.1.0) reached the registry 4 months ago.
Which apps can use it?
Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT on the web (full MCP on Business and above; Pro read-only).
What can I use instead?
In the same category: OpenSEO, Exa, Mockserver, Microsoft Learn MCP, Docs
Similar alternatives
Same category, other makers, commands already checked. Official ones first, then by stars.
Reading a card:↓ Downloads per weeki★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi
Exa
Connect AI agents to Exa for web search, content fetching, and multi-step research.
Mockserver
Mock, record/replay, verify and chaos-test any HTTP, REST, gRPC or LLM dependency over MCP.
Microsoft Learn MCP
Official Microsoft Learn MCP Server – real-time, trusted docs & code samples for AI and LLMs.
Docs
Search and read Empryo's documentation. Read-only, no auth, no local access.
- OpenSEO — Runs in the cloud, nothing to install · No key needed
- Exa — Runs in the cloud, nothing to install · No key needed · In Claude’s directory
- Mockserver — Installs on your computer · No key needed
- Microsoft Learn MCP — Runs in the cloud, nothing to install · No key needed · In Claude’s directory
- Docs — Runs in the cloud, nothing to install · No key needed
README from the maker
Open the README
Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.
AtCoder MCP Server
Find and read past AtCoder problems through MCP, locally or over hosted HTTP.
Quick Start
Add the hosted server to your MCP configuration:
{"servers": { "atcoder": { "type": "http", "url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp" } } }
The endpoint accepts anonymous read requests. It does not need an API key, Cookie, or judge account.
Then ask:
Fetch AtCoder problem abc086_a and show its samples.What It Can Do
| Tool | Purpose |
|---|---|
oj_capabilities | Report the available AtCoder read operations and transport. |
oj_health | Report process readiness and the latest upstream read. |
oj_fetch_problem | Fetch one past problem by canonical URL or contest/task id. |
oj_search_problems | Resolve an exact task URL or contest/task identifier. |
Run Locally
Requires Node.js 22 or newer.
npm cinpm run check npm run build node packages/atcoder/dist/index.js
MCP client configuration from a source checkout:
{"servers": { "atcoder": { "type": "stdio", "command": "node", "args": ["/absolute/path/packages/atcoder/dist/index.js"] } } }
Tagged GitHub releases attach a standalone npm tarball.
Availability
- Hosted MCP:
https://api.ksrnyx.top/oj-mcp/atcoder/mcp - Official MCP Registry:
io.github.ketherworks/atcoder, described byserver.json - Health status: see the repository homepage or call
oj_health
Source and Safety
This standalone release is generated from the reviewed Competitive Programming MCP source. The release package bundles the shared OJ contract implementation, so its runtime does not depend on unpublished workspace packages.
Platform Rules
Do not use this server during ongoing ABC, ARC, or AGC contests. AtCoder's current generative-AI rules generally prohibit that use. This project is intended for practice with past problems. It is unofficial and is not affiliated with or endorsed by AtCoder Inc. Problem content remains subject to the AtCoder Terms of Use.
The server exposes no run or submit tool. It accepts no judge account credentials. See SECURITY.md for the security boundary and PROVENANCE.md for the canonical source revision.
Development
npm cinpm run check npm run pack:check npm run deploy:dry
License
Adapter source code is MIT licensed. Judge problem content and trademarks are not relicensed by this repository.