Proposition 65 MCP Server

by toolstop Your server? Claim it

not responding

Proposition 65 is listed as active in the registry but did not answer our last check. 16 installs a week from npm. It exposes 4 tools. Last commit 17 Sep 2026.

Is a chemical on California's Proposition 65 list, and does it need a warning?

The author archived this repository on GitHub, meaning it is no longer maintained.

Installs per day peak 4 · avg 1 · +23% w/w

a month agotoday

Uptime history 90 days of history · worst day 0%

90 days agonow

0.0%

Uptime 24h

0 of 91 checks

Tools

read from the server

9 ms

Response time

average over 24h

Installs / week

npm and PyPI

Proposition 65 does not always answer

Over the last week it answered 0.0% of our checks. We check every 15 minutes, so you hear about the next outage within the hour — not from your users.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 12 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add prop65 --transport http https://prop65.toolstop.dev

Settings → Connectors → Add custom connector, then paste this address

https://prop65.toolstop.dev

~/.codex/config.toml

[mcp_servers.prop65]
url = "https://prop65.toolstop.dev"

.cursor/mcp.json

{
  "mcpServers": {
    "prop65": {
      "url": "https://prop65.toolstop.dev"
    }
  }
}

.vscode/mcp.json

{
  "servers": {
    "prop65": {
      "type": "http",
      "url": "https://prop65.toolstop.dev"
    }
  }
}

Available tools 4

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

prop65

check_prop65

Look up a chemical by CAS number or name and report whether it is on California's Proposition 65 list. Use this when deciding whether a product sold into California needs a warning label. Returns every matching entry with the toxicity endpoint, the listing mechanism, the date listed and the safe-harbour level where one has been adopted, plus whether the entry has since been delisted. A `not_found` result does not mean the chemical is safe or unregulated: it means this edition of this one list has no entry under that name or number.

search_prop65

Search the Proposition 65 list for chemicals whose name contains a fragment. Use this when you do not have an exact name or a CAS number, or to survey a family of related substances. Returns matching chemicals with their CAS numbers, toxicity endpoints, listing dates and delisted flags, capped at a limit with `truncated` set when there were more. It searches names only, so it will not find a chemical listed under a synonym you did not search for, and a result here is not a determination that a warning is required.

describe

describe_prop65_list

Report the size and edition of the embedded Proposition 65 list, and what the listing-mechanism codes mean. Use this to check how current the data is before relying on a lookup, or to interpret the `AB`, `SQE`, `FR` and `LC` codes on an entry. Returns counts of total, active and delisted entries, how many carry a CAS number, and the edition date. It reports on the data only and cannot tell you whether any product requires a warning.

recent

list_recent_listings

List the chemicals added to Proposition 65 on or after a given year. Use this to find recent additions, which matters because a warning is generally required twelve months after a chemical is listed, so a new entry starts a compliance clock. Returns active listings only, newest first, with their dates, and reports how many entries carry no parseable date and are therefore missing from the answer. It does not tell you whether any particular product is affected.

Endpoints

URL	Transport	State	Latency	Checked
https://prop65.toolstop.dev	streamable-http	answering	9 ms	12 min ago

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Proposition 65 — questions

Answers built from our own checks of this server.

What can Proposition 65 do?

It exposes 4 tools, read directly from the server on our last check. Among them: check_prop65, describe_prop65_list, list_recent_listings, search_prop65. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →

Is Proposition 65 working right now?

We send a real MCP handshake every 15 minutes. Over the last 24 hours 0 of 91 checks got a reply (0.0%), average response time 9 ms. The bar chart above shows every period we have measured.

Is Proposition 65 still maintained?

The author archived this repository on GitHub, meaning it is no longer maintained. We show this because it changes what you can expect: an unmaintained server may keep answering for months and then stop without warning.

The registry lists Proposition 65 as active — why does it not respond?

The official MCP registry stores what the author submitted; it does not verify that the server still runs. We check the endpoint ourselves, and this one does not answer. Catalogues that copy the registry without checking will show it as working.

How do I connect Proposition 65?

Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.

Does Proposition 65 need an API key?

No. Proposition 65 completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 4 of them are readable on this page. This is what we observed, not what the docs claim.

How many people use Proposition 65?

The npm package @toolstop/prop65 was installed 16 times in the last week. Week over week that is +23%. We show installs rather than GitHub stars on purpose: a star is a bookmark, an install is someone actually running it.

Is Proposition 65 open source?

The code is open source: it is published under the MIT licence, written in JavaScript and 0 stars on GitHub. The licence covers the code in the repository, not the hosted service at prop65.toolstop.dev, which runs on its operator's own terms.