AtCoder MCP Server

io.github.ketherworksPublished by GitHub account ketherworksv0.1.0Updated Oct 24, 2026

Search AtCoder problems and fetch public problem statements through MCP.

VerifiedStreamable HTTPWeb executableWeb Search & Scraping Knowledge & Memory

Server details

Identifier: io.github.ketherworks/atcoder
Transport: Streamable HTTP
Runtime: Web executable
Trust: Verified
Published: Sep 16, 2026

Security note

MCP servers receive tool arguments from a conversation and may perform external actions. Review what a server can do before you enable it, and give it only the access it needs.

The registry verified the GitHub account ketherworks for this listing. That does not show the account is the product's maker.

SourceWeft's checks cover whether the listing is complete and the endpoint answered; they do not review the server's code or what its tools do.

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Overview

AI-generated overview

An unofficial AtCoder MCP server that lets an assistant look up and fetch public past competitive-programming problem statements.

What you can do: Report the server's supported anonymous read operations and explicitly unsupported operations, plus local readiness and the last observed AtCoder page-read status without probing upstream. Resolve exactly one contest/task identifier or canonical AtCoder task URL to a problem. Fetch a single public problem statement as sanitized HTML with math, samples, limits, hashes and source provenance preserved.
When to use it: Useful when practicing with past AtCoder problems and you want an assistant to pull a specific problem statement and its samples into the conversation. It is not for free-text search, catalog browsing, running code, or submitting solutions.
Requirements: Either the hosted HTTP endpoint, which accepts anonymous read requests with no API key, cookie or judge account, or a local run from a source checkout with Node.js 22 or newer. Network access to AtCoder is needed for problem reads.

Before you install

Only exact contest/task identifiers or canonical task URLs are accepted; free-text and catalog crawling are unsupported. The server exposes no run or submit tool and takes no judge account credentials. Do not use it during ongoing ABC, ARC or AGC contests, since AtCoder's generative-AI rules generally prohibit that; it is unofficial and problem content remains subject to AtCoder's Terms of Use.

Installation

In SourceWeft

Open AtCoder MCP Server in the dashboard and add it to a workspace.
Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/io.github.ketherworks%2Fatcoder/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "atcoder": {
      "type": "http",
      "url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"
    }
  }
}

README

AtCoder MCP Server

简体中文

Find and read past AtCoder problems through MCP, locally or over hosted HTTP.

Quick Start

Add the hosted server to your MCP configuration:

json

{  "servers": {    "atcoder": {      "type": "http",      "url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"    }  }}

{  "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:

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.

MCP client configuration from a source checkout:

json

{  "servers": {    "atcoder": {      "type": "stdio",      "command": "node",      "args": ["/absolute/path/packages/atcoder/dist/index.js"]    }  }}

{  "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 by server.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

License

Adapter source code is MIT licensed. Judge problem content and trademarks are not relicensed by this repository.

Source: README.md at commit 9743892

Tools

oj_capabilities

AtCoder Provider Capabilities

Report the audited anonymous AtCoder read surface and explicitly unsupported operations.

Takes no parameters.

oj_health

AtCoder Provider Health

Report local readiness and the latest observed AtCoder page-read status without probing upstream.

Takes no parameters.

oj_fetch_problem

Fetch AtCoder Problem

Fetch 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.

Takes no parameters.

oj_search_problems

Find Exact AtCoder Problem

Resolve exactly one contest/task id, atcoder:contest/task id, or canonical task URL. Free-text and catalog crawling are not supported.

ParameterslimitrequiredqueryrequiredlocaleplatformrequiredrequestIdrequiredschemaVersionrequired

Version history

v0.1.0LatestSep 16, 2026

Score

100% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

Reached in the last 30 daysRequired25 pts
Auth declaredRequired10 pts
Tools listedRequired15 pts
DescriptionRequired15 pts
Logo10 pts
Documentation15 pts
License10 pts