Free GTM & Deliverability Tools MCP

Connect

Server

WarmInboxes Free MCP

URL

https://warminboxes.com/mcp

Transport

Streamable HTTP

Authentication

None. No account, no API key

Install name

warminboxes-free

Sizing-only view

https://warminboxes.com/mcp/planner (Fleet Planner)

For a client that reads a JSON config (Claude Desktop, Cursor and the like):

{
  "mcpServers": {
    "warminboxes-free": {
      "url": "https://warminboxes.com/mcp"
    }
  }
}

Step-by-step for each assistant is on the Deliverability Agent page.

Over HTTP

Each tool is also an endpoint at https://warminboxes.com/.netlify/functions/<endpoint>. Send the parameters as a query string on GET, or as a JSON body on POST (use POST for pasted headers, HTML or CSV). CORS is open. The full spec is openapi.json.

curl "https://warminboxes.com/.netlify/functions/check-deliverability?domain=example.com"

Every tool

MCP name, HTTP endpoint and parameters. Parameters marked * take a list.

Machine-readable files

/tools.json

Every free tool, and whether an assistant can run it and with which MCP tool

/openapi.json

The HTTP endpoints as an OpenAPI 3.1 spec

/llms.txt

The site for language models, with every tool and endpoint

/facts.json

Counts, delivery times and policies, generated from the site’s source

/research.json

The studies with their IDs, data files and citations

/changelog.json

What changed, by week

Limits

• Every tool is read-only. It does not send email, buy inboxes or change your DNS.
• The Spamhaus DBL needs a paid key and is not queried. Asked about it, the answer says "not checked" and links Spamhaus’s own lookup; it never reports a domain as clean there.
• Authentication checks cannot guarantee inbox placement, and there are no invented reputation scores: mailbox providers keep those private.
• A free daily limit applies, counted in distinct domains. Checking a domain again the same day does not count again.
• Pasted copy, headers and CSVs are processed to answer and not stored.