Using the Signal8 MCP Server with Claude, Cursor and Other AI Tools

The short version

The Model Context Protocol (MCP) is a standard way for an AI assistant to call external tools. Signal8 publishes an MCP server that gives an assistant such as Claude or Cursor read-only access to Signal8's company, SEC filing, ownership, dilution, premarket and congressional-trading data. Instead of pasting numbers into a chat, you ask a question and the assistant calls the right Signal8 tool itself.

There are two ways to run it: the hosted server at https://mcp.signal8.ai/mcp, which needs nothing installed, and the local package @signal8ai/mcp, which runs on your machine through npx. Both read data from the same Signal8 API. Using the tools requires Signal8 Pro, because tool calls are authenticated with a Pro API key or a Pro account sign-in.

What you need

• A Signal8 account on the Pro plan ($59 a month or $588 a year).
• For key-based setups, an API key. Keys are created in the API keys tab of the MCP page or on the developer page. Live keys start with sk_live_.
• An MCP-capable client: Claude (web, desktop or Claude Code), Cursor, VS Code, or another client that supports MCP servers.

Connecting Claude on the web or desktop

The MCP page walks through the hosted connector flow for Claude:

1. In Claude, open Settings → Connectors.
2. Click Add custom connector.
3. Paste the server URL https://mcp.signal8.ai/mcp and connect.

There is no key to paste in this flow. Claude opens a Signal8 sign-in page and you authorize the connection with your account. If the account is not on Pro, the authorization is refused with an upgrade prompt.

Connecting with a config file or the command line

Claude Code

One command registers the hosted server, with your key in an authorization header:

claude mcp add --transport http signal8 https://mcp.signal8.ai/mcp \
  --header "Authorization: Bearer sk_live_YOUR_KEY"

Claude Desktop, Cursor and other clients (local package)

Add this block to the client's MCP configuration. For Claude Desktop that is claude_desktop_config.json; for Cursor it is mcp.json.

{
  "mcpServers": {
    "signal8": {
      "command": "npx",
      "args": ["-y", "@signal8ai/mcp"],
      "env": { "SIGNAL8_API_KEY": "sk_live_YOUR_KEY" }
    }
  }
}

The package needs Node.js 18 or later. It reads two environment variables: SIGNAL8_API_KEY (required for tool calls) and SIGNAL8_API_URL (optional, defaults to the public Signal8 API). If the key is missing, the server still starts in a discovery-only mode: the client can list the tools, but every tool call is rejected until a key is set.

Hosted server from a config file

Clients that accept HTTP servers can point at the hosted endpoint instead of running the package:

{
  "mcpServers": {
    "signal8": {
      "type": "http",
      "url": "https://mcp.signal8.ai/mcp",
      "headers": { "Authorization": "Bearer sk_live_YOUR_KEY" }
    }
  }
}

The MCP page also has one-click Add to Cursor and Add to VS Code buttons that install this hosted configuration with a placeholder key, which you then replace.

What the tools cover

The server exposes around a hundred read-only tools, grouped roughly as follows:

The assistant chooses tools from their descriptions, so you rarely need to name one. Naming it helps when you want a specific dataset.

Ten example prompts

Each prompt lists the tools an assistant would typically reach for.

1. "Look up the company profile and current quote for AAPL." (get_company_profile, get_quote)
2. "Is there a Signal8 dilution analysis for this ticker? If so, summarize its dilution risk score and say which components were not measured." (get_dilution_coverage, get_dilution_risk)
3. "How much could this company raise off its shelf right now under the baby shelf rule?" (get_baby_shelf_capacity)
4. "List the warrants in this company's dilution snapshot, with exercise prices and the filing each figure came from." (get_dilution_instruments)
5. "Show the last ten Form 4 transactions by insiders at this company, and flag any open-market purchases." (get_insider_transactions)
6. "Which companies have the shortest estimated cash runway?" (screen_must_raise, get_cash_runway_calendar)
7. "Find 8-K filings that mention 'securities purchase agreement' for this company in the last 90 days." (search_sec_filings, search_filing_text)
8. "What is on the premarket scanner right now, and which names have unusually high relative volume?" (get_premarket_scanner, get_rvol_history)
9. "Which members of Congress have disclosed trades in this ticker?" (get_senate_trades_by_ticker)
10. "Which reverse splits are scheduled for the coming week?" (get_upcoming_reverse_splits)

Limits and errors

Tool calls count against the same limits as direct API calls, measured per key. On the Pro plan that is 120 requests per minute and 10,000 per day, with up to three keys. When a limit is hit the API returns HTTP 429, and the assistant usually reports that it was rate limited. A 401 means the key is missing, invalid or revoked; a 403 with FEATURE_NOT_AVAILABLE means the account's plan does not include that data. See the API quickstart for the full picture.

FAQ

Do I need to install anything to use Signal8 with Claude?

No. The hosted server at mcp.signal8.ai needs no installation. In Claude on the web or desktop you add it as a custom connector under Settings, Connectors, and sign in with your Signal8 account. Installing the local npm package is optional and mainly useful for clients that only support locally run servers.

Does the Signal8 MCP server work without Pro?

The server will start and list its tools without a key, but tool calls require authentication with a Pro account. Free accounts cannot create API keys, and the sign-in connector flow refuses accounts that are not on Pro with an upgrade prompt. Pro is $59 a month or $588 a year.

Can the MCP server place trades or change anything in my account?

No. Every tool is read-only. The server retrieves company data, filings, ownership, dilution and political-trading data. It has no tools for orders, watchlist changes or account settings.

Why did the assistant say a dilution figure was not available?

Dilution analysis covers small-cap issuers and not every company has been analysed. The coverage tool reports whether an analysis exists, and the other dilution tools mark figures that could not be measured or verified. An unavailable figure means not measured, not zero, so the assistant should not describe the company as having none of that instrument.