Connect Litmus and your agent gets 3 tools, among them check_server, list_servers, request_grade. It answers at https://polygraph.so/api/mcp over streamable HTTP, and it listed its tools to an anonymous client, so no sign-in was needed for that. Our probes reached it 6 of 6 times since 11 September 2026; the last check, on 23 October 2026, succeeded.
Grade MCP servers A to F with the open behavioral litmus. npm: full toolset; hosted: lookups only.
Description as the publisher wrote it.
| Tool | What it does |
|---|---|
check_server | Read a server's published behavioral grade (A-F) from polygraph.so in under a second; no execution. The pre-flight check before recommending or installing an MCP server. On a miss it returns not_available (unevaluated: neither safe nor unsa Inputs: server_ref |
list_servers | Servers with a published polygraph grade, sorted A-first then by ref. Returns up to `limit` rows starting at `offset` (default limit 25, capped at 100 per call); `grade` restricts to one letter. `summary` always covers the full graded corpu Inputs: grade, limit, offset |
request_grade | Hosted grading is discontinued. This tool returns gone. Existing published grades remain available via check_server / list_servers. To grade a server yourself, run the open harness: npx -y -p @polygraphso/litmus polygraphso-litmus litmus <s Inputs: server_ref |
Every block below points at https://polygraph.so/api/mcp. Pick your client and copy.
claude mcp add --transport http litmus https://polygraph.so/api/mcp
{
"mcpServers": {
"litmus": {
"command": "npx",
"args": ["-y", "mcp-remote", "https://polygraph.so/api/mcp"]
}
}
}{
"mcpServers": {
"litmus": {
"url": "https://polygraph.so/api/mcp"
}
}
}{
"servers": {
"litmus": {
"type": "http",
"url": "https://polygraph.so/api/mcp"
}
}
}{
"context_servers": {
"litmus": {
"url": "https://polygraph.so/api/mcp"
}
}
}{
"mcpServers": {
"litmus": {
"serverUrl": "https://polygraph.so/api/mcp"
}
}
}{
"mcpServers": {
"litmus": {
"url": "https://polygraph.so/api/mcp"
}
}
}name: Litmus
version: 0.0.1
schema: v1
mcpServers:
- name: Litmus
type: streamable-http
url: https://polygraph.so/api/mcp{
"mcpServers": {
"litmus": {
"httpUrl": "https://polygraph.so/api/mcp"
}
}
}{
"mcpServers": {
"litmus": {
"type": "http",
"url": "https://polygraph.so/api/mcp"
}
}
}{
"mcpServers": {
"litmus": {
"url": "https://polygraph.so/api/mcp"
}
}
}goose://extension?url=https%3A%2F%2Fpolygraph.so%2Fapi%2Fmcp&type=streamable_http&id=litmus&name=Litmus
It answered our last check on 23 October 2026 in 315 ms. Over 6 checks since 11 September 2026 it answered 6. Status here comes from Neuronto's own probes, not from the publisher.
3, as returned by the server's own tools/list on 18 September 2026: check_server, list_servers, request_grade.
It answered our last check on 23 October 2026 in 315 ms. Over 6 checks since 11 September 2026 it answered 6.
Put the server under mcpServers in ~/.cursor/mcp.json with the URL https://polygraph.so/api/mcp. The exact JSON is above, with the same setup for Claude Code, Claude Desktop, VS Code, Windsurf, Zed, Gemini CLI and the rest.
It listed its tools to an anonymous client, so reading the tool list needs no key. Individual tools can still ask for credentials in their own inputs.
Publisher: io.github.polygraphso. Endpoint host: polygraph.so. ARD identifier: urn:air:io.github.polygraphso:mcp:litmus.
First indexed 10 September 2026. The tools are exactly what the server returned; nothing on this page
is inferred from its name. Ranking in Neuronto search is never for sale.