WarmInboxes Free MCP: Fleet Planner

Fleet estimate from a recipient list

plan_from_list

Read-onlyIdempotent

Estimates a sending fleet for a recipient list. Looks up the MX records of up to 100 recipient domains (or addresses) to measure the provider mix, then sizes a Google Workspace pool for the Google-hosted recipients and an Azure pool for everyone else (Microsoft 365, other providers and gateway-protected domains, with a warning for gateways); microsoftEsp: "microsoft" moves the Microsoft recipients to a Microsoft 365 pool, only when the person asks for it. Returns inbox count, domain count, per-inbox pace and monthly cost for each pool, plus totals, the routing rule and the placement-log figures behind it. Domains with no mail server are left out and named. For a longer list, send a sample: the estimate follows the provider split, not the list length. Assumes no reserve capacity. A planning estimate only: it does not provision or order anything. The result describes how an order is placed: a first order in the WarmInboxes app, later ones through WarmInboxes Infrastructure MCP.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "domains": "<domains>",
      "emailsPerDay": "<emailsPerDay>"
    },
    "name": "plan_from_list"
  }
}

Input Schema

Name	Required	Description
`billing`	No	Prewarmed commitment length. Longer is cheaper. Defaults to monthly.
`domains`	Yes	Up to 100 recipient domains or email addresses. Deduplicated.
`rotation`	No	Rest half the fleet at any moment, which doubles the inboxes bought. Defaults to false.
`prewarmed`	No	true for prewarmed inboxes (sending within 48–72 hours of delivery), false for fresh (21-day warmup, cheaper). Defaults to true.
`emailsPerDay`	Yes	Target cold emails per day across the whole list, e.g. 1500.
`microsoftEsp`	No	Which pool carries the Microsoft recipients. Defaults to azure; use microsoft only when the person asks for Microsoft 365 inboxes.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 10, 2026

TDQS

A4.6/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly/idempotent/non-destructive, and the description still adds substantial behavioral context beyond them: no provisioning or ordering, no reserve capacity assumed, unhosted domains excluded and named, gateway-protected domains flagged with a warning, and a documented return structure including the routing rule and placement-log figures.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Purpose, mechanism, output, caveats and follow-up are ordered front to back, so the key facts arrive first. It is dense, with a couple of long parenthetical clauses and an inline 'microsoftEsp' gloss that could have been tightened, but nearly every sentence carries information an agent needs.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a six-parameter planning tool with no output schema, the description covers the alternative correctly: what it computes, what it returns, which recipients land where, what is excluded, and what it deliberately does not do. An agent could call this and interpret the result with no further information.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning: it reiterates the 100-item/dedup limit, gives the decision rule for microsoftEsp ('only when the person asks for it'), and explains why sampling rather than expanding the list is correct. The rotation and billing parameters are left to the schema, so it is not fully additive.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The first sentence gives a specific verb and resource ('Estimates a sending fleet for a recipient list'), and the description goes on to state the mechanism (MX lookup of up to 100 domains, provider mix, Google vs Azure pool sizing). This makes it easy to distinguish from sibling planning tools such as plan_infrastructure, plan_rotation or quote_inboxes, which do not take a recipient list.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It specifies when a parameter variant applies ('microsoft only when the person asks for it'), how to handle long lists ('send a sample: the estimate follows the provider split, not the list length'), and the boundary of the tool ('A planning estimate only: it does not provision or order anything'). It also explains how to act on the result (first order via the WarmInboxes app, later ones via Infrastructure MCP), though it never names the sibling planning tools it should be preferred over.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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