AtCoder MCP Server
REMOTE · API.KSRNYX.TOP · SCANNED SEP 20
Search AtCoder problems and fetch public problem statements through MCP.
Available components
How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. How we score → Why this is hard to score →
Endpoint Security74
- The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
- No authorisation is required to call this server. Every tool declares its destructiveHint and none is destructive, so open access doesn't expose one. See how to fix → View diagnostics → Partial
- HTTPS is enforced; there's no plaintext access path. View diagnostics → Pass
- HSTS check failed: the Strict-Transport-Security header is absent. See how to fix → View diagnostics → Fail
- DNSSEC check failed: this domain isn't protected by DNSSEC. See how to fix → View diagnostics → Fail
Transport & Reachability100
- Verified streamable-http transport via a live MCP handshake. View diagnostics → Pass
Schema Quality & AI Usability69
- AI-judged instruction clarity (good).Pass
- Tool/resource definitions use about 173 tokens (~43/item across 4 items; 4 tools + 0 resources), lean.Pass
- Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management100
- No destabilizing schema changes in the last 30 days.Pass
Tool Coverage71
- 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
- 0% of tool parameters carry a description.Fail
- Structured output schemas are declared (100% of tools); any adoption earns full credit.Pass
Tool Safety100
- No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
- We read all 4 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
- An AI judge read all 4 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities100
- Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.Pass
How do I install the AtCoder MCP Server server?
AtCoder MCP Server is a hosted endpoint at https://api.ksrnyx.top/oj-mcp/atcoder/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.
remote · api.ksrnyx.top
claude mcp add --transport http ketherworks-atcoder 'https://api.ksrnyx.top/oj-mcp/atcoder/mcp'
{
"mcpServers": {
"ketherworks-atcoder": {
"url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"
}
}
} {
"servers": {
"ketherworks-atcoder": {
"type": "http",
"url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"
}
}
} [mcp_servers.ketherworks-atcoder] url = "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"
{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"ketherworks-atcoder": {
"type": "remote",
"url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp",
"enabled": true
}
}
} openclaw mcp add ketherworks-atcoder --url 'https://api.ksrnyx.top/oj-mcp/atcoder/mcp' --transport streamable-http
mcp_servers:
ketherworks-atcoder:
url: "https://api.ksrnyx.top/oj-mcp/atcoder/mcp" {
"McpServers": {
"ketherworks-atcoder": {
"Transport": "http",
"Url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"
}
}
} assistant mcp add ketherworks-atcoder -t streamable-http -u 'https://api.ksrnyx.top/oj-mcp/atcoder/mcp'
{
"mcpServers": {
"ketherworks-atcoder": {
"type": "http",
"url": "https://api.ksrnyx.top/oj-mcp/atcoder/mcp"
}
}
} The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.
Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.
- 26 Aug 26 +1
- We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
- 25 Aug 26 +1
- Stability: 0.97 → pass security
- 24 Aug 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 93 to 97. That category is still filling its 30-day observation window: 28 days of observed history at the previous scan, 29 at this one. The score rises as the window fills, whether or not the server changes.
- 11 Aug 26 0
- We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
- 31 Jul 26 0
- We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
- 27 Jul 26 0
- We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
- 26 Jul 26 0
First indexed and scored.
Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.
Captured 20 Sept 2026 · Probed https://api.ksrnyx.top/oj-mcp/atcoder/mcp
TLS valid
Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .
| Subject | Issuer | Valid from | Valid until | Key | Signature | Serial |
|---|---|---|---|---|---|---|
| CN=api.ksrnyx.top | CN=YE1,O=Let's Encrypt,C=US | 29 Jul 2026 | 27 Oct 2026 | ECDSA 256 | ECDSA-SHA384 | 6a7a5a686c72cd4427700cd9cfc905ebd66 |
| SANs: api.ksrnyx.top | ||||||
| CN=YE1,O=Let's Encrypt,C=US (CA) | CN=Root YE,O=ISRG,C=US | 3 Sept 2025 | 2 Sept 2028 | ECDSA 384 | ECDSA-SHA384 | 5ddd70dd31f801c85c186a7a04b80afe |
| CN=Root YE,O=ISRG,C=US (CA) | CN=ISRG Root X2,O=Internet Security Research Group,C=US | 13 May 2026 | 2 Sept 2032 | ECDSA 384 | ECDSA-SHA384 | 872165fc34b6e5fba8add5b3705fb53a |
| CN=ISRG Root X2,O=Internet Security Research Group,C=US (CA) | CN=ISRG Root X1,O=Internet Security Research Group,C=US | 13 May 2026 | 2 Sept 2032 | ECDSA 384 | SHA256-RSA | 6c8f1dc727c7117f7baf853ac980f9cd |
Background: What to check on a remote MCP endpoint →
DNSSEC insecure
Validation of api.ksrnyx.top. — Not signed
| Zone | DS | Keys | Algorithms | Outcome |
|---|---|---|---|---|
| . | trust_anchor | 20326, 38696 | 8, 8 | Verified |
| top. | present | 26780 | 8 | Verified |
| ksrnyx.top. | absent | Unsigned (proven) parent-signed NSEC/NSEC3 proves an unsigned delegation |
Authentication No authorisation required
The endpoint answered without asking for a token. Anyone who knows the URL can reach it.
| Result | No authorisation required |
|---|---|
| HTTP status | 200 |
Background: How OAuth 2.1 works in the 2026 MCP spec →
Transports 2 probes
| Transport | URL | Outcome | Status | Location |
|---|---|---|---|---|
| streamable-http | https://api.ksrnyx.top/oj-mcp/atcoder/mcp | Verified | 200 | |
| http (plaintext) | http://api.ksrnyx.top/oj-mcp/atcoder/mcp | HTTPS enforced | 301 | https://api.ksrnyx.top/oj-mcp/atcoder/mcp |
The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →
oj_capabilities AtCoder Provider Capabilities ~22
Report the audited anonymous AtCoder read surface and explicitly unsupported operations.
Input schema present but exposes no named parameters.
Structured output declared, but exposes no named fields.
No examples provided.
oj_fetch_problem Fetch AtCoder Problem ~45
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.
Input schema present but exposes no named parameters.
Structured output declared, but exposes no named fields.
No examples provided.
oj_health AtCoder Provider Health ~24
Report local readiness and the latest observed AtCoder page-read status without probing upstream.
Input schema present but exposes no named parameters.
Structured output declared, but exposes no named fields.
No examples provided.
oj_search_problems Find Exact AtCoder Problem ~82
Resolve exactly one contest/task id, atcoder:contest/task id, or canonical task URL. Free-text and catalog crawling are not supported.
| Name | Type | Req | Description |
|---|---|---|---|
| limit | integer | yes | – |
| locale | string | – | – |
| platform | string | yes | – |
| query | string | yes | – |
| requestId | string | yes | – |
| schemaVersion | string | yes | – |
Structured output declared, but exposes no named fields.
No examples provided.
What is the AtCoder MCP Server server?
AtCoder MCP Server is listed in the public MCP registry as io.github.ketherworks/atcoder. Search AtCoder problems and fetch public problem statements through MCP. This page covers its hosted endpoint (https://api.ksrnyx.top/oj-mcp/atcoder/mcp).
Is the AtCoder MCP Server server safe to use?
AtCoder MCP Server scores 82 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.
What tools does the AtCoder MCP Server server expose?
AtCoder MCP Server exposes 4 tools: oj_capabilities, oj_health, oj_fetch_problem, oj_search_problems. Their descriptions and schemas cost roughly 173 tokens of context every time the server is loaded.
Does the AtCoder MCP Server server require authentication?
No. We connected to AtCoder MCP Server without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.
Is the AtCoder MCP Server server still maintained?
AtCoder MCP Server is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.