Signal8 MCP server (@signal8ai/mcp)

Signal8 MCP server for SEC EDGAR filings, Form 4 insider trades, 13F institutional holdings, congressional STOCK Act trades and dilution data. It gives Claude, Cursor and any other Model Context Protocol client 113 read-only tools over the Signal8 API.

• Hosted: https://mcp.signal8.ai/mcp (Streamable HTTP, API key or OAuth sign-in)
• Local: npx -y @signal8ai/mcp (stdio)
• Registry name: ai.signal8/mcp in the official MCP Registry

What works without an API key: the three Signal8 Academy tools, search_learn_guides, get_learn_guide and define_term (plain-English guides to dilution, SEC filings and market structure, plus a glossary), and the signal8://learn resources. On the local server they work with SIGNAL8_API_KEY unset. On the hosted server they need a signed-in Signal8 account, which can be a free one.

What needs Signal8 Pro: every other tool. API and MCP access are included with Signal8 Pro ($59/mo or $588/yr): 120 requests per minute, 10,000 requests per day, up to 3 API keys, no per-call charges. Upgrade at signal8.ai/pro and create a key at signal8.ai/developer/api-keys. Without a key the server still starts and lists its tools; calls to the other tools return an API_KEY_REQUIRED error.

Quick start

Claude.ai and Claude Desktop (no key to copy)

Settings > Connectors > Add custom connector, paste https://mcp.signal8.ai/mcp, then sign in with your Signal8 account when Claude asks.

Claude Desktop with an API key (local server)

Add to claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/claude_desktop_config.json, Windows: %APPDATA%\Claude\claude_desktop_config.json):

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

Leave out the env block to use only the Academy tools.

Claude Code

Hosted server, sign in with OAuth (run /mcp in Claude Code to authenticate):

claude mcp add --transport http signal8 https://mcp.signal8.ai/mcp

Hosted server with an API key:

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

Local server:

claude mcp add signal8 -e SIGNAL8_API_KEY=sk_live_your_key_here -- npx -y @signal8ai/mcp

Cursor

Add to .cursor/mcp.json in your project (or ~/.cursor/mcp.json for all projects). Hosted:

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

Local:

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

Cline

Open Cline's MCP Servers panel, choose Configure MCP Servers, and add this to cline_mcp_settings.json (Cline CLI: ~/.cline/data/settings/cline_mcp_settings.json):

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

Leave out the env block to use only the Academy tools. Step-by-step notes for agents are in llms-install.md.

Any other MCP client

SIGNAL8_API_KEY=sk_live_your_key_here npx -y @signal8ai/mcp

or point a Streamable HTTP client at https://mcp.signal8.ai/mcp with Authorization: Bearer sk_live_....

Tools (113)

This table lists every tool the server registers. Each tool's full input schema and description are returned by tools/list.

SEC EDGAR filings (12)

Form 4 insider trades (6)

13F institutional holdings and ownership (12)

Congressional and executive-branch trades (STOCK Act) (22)

Campaign finance (FEC) (3)

Dilution and cash runway (11)

Companies, prices and fundamentals (19)

Analysts (5)

Market-wide, calendars and scanners (20)

Signal8 Academy (no API key) (3)

How it compares

• SEC EDGAR APIs (sec.gov, data.sec.gov). Free and keyless; SEC asks for a declared User-Agent and at most 10 requests per second. They return filings and XBRL facts as EDGAR publishes them. Open-source EDGAR MCP servers wrap these APIs and share those properties.
• Signal8. Requires a Pro API key for everything except the Academy tools. Adds data that EDGAR does not publish in parsed form: Form 3/4/5, 13F and Schedule 13D/G parsed into rows, 13F quarter-over-quarter diffs, a combined ownership view, dilution instruments (warrants, convertibles, ATMs, shelves) with the filing sentence each figure was read from, cash runway estimates, and sources outside EDGAR: congressional and executive-branch STOCK Act disclosures, FEC campaign finance, Federal Register executive orders, FINRA uplistings, trading halts, quotes and intraday bars.

Resources

"Key needed" applies to the local server. The hosted server asks for a key or a signed-in account before any resources/read or tool call.

Academy tracks: dilution, filings, market-structure, signal8. Academy content is fetched from GET /api/v1/public/learn/*, so guide updates appear without a package release.

Prompts (4)

Hosted endpoint

POST https://mcp.signal8.ai/mcp
Authorization: Bearer sk_live_your_key_here
Content-Type: application/json

Clients that support MCP OAuth need no key: the server advertises its authorization server at https://mcp.signal8.ai/.well-known/oauth-protected-resource (OAuth 2.1 with PKCE and dynamic client registration, issued by https://api.signal8.ai). Unauthenticated initialize and tools/list are answered; tool calls need a key or a signed-in account. OAuth connections have the same Pro requirement and rate limits as API keys.

Environment variables (local server)

Programmatic usage

import { createMcpServer, Signal8ApiClient } from '@signal8ai/mcp';

const client = new Signal8ApiClient({
  baseUrl: 'https://api.signal8.ai/api/v1/public',
  apiKey: 'sk_live_xxx',
});

const server = createMcpServer(client);
// Connect to any MCP transport...

Links

• Product page: signal8.ai/mcp
• API docs: signal8.ai/developer/docs
• Changelog: CHANGELOG.md

License

MIT, see the LICENSE file. Copyright (c) 2025-2026 Signal8 AI, Inc.

Use of the hosted Signal8 API and data is additionally governed by the Signal8 Terms of Service.