hail

Official

by hail-hq

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Python

Hybrid

List email domains

list_email_domains

Read-onlyIdempotent

List the addresses this workspace can send email from. Call this BEFORE send_email when you do not already know the from_ address — do not guess a domain.

Instructions

List the addresses this workspace can send email from. Call this BEFORE send_email when you do not already know the from_ address — do not guess a domain.

    Returns ``{"items": [...], "next_cursor": ..., "default_from": ...}``.
    Each item carries ``domain``, ``kind`` (``"custom"`` or
    ``"hail_mail"``) and ``verification_status``; only ``"verified"``
    rows can send. A ``custom`` item's ``domain`` is a bare DNS name
    that accepts any local-part (``sales@acme.com``); a ``hail_mail``
    item's ``domain`` is already a full address.

    ``default_from`` is the address a ``send_email`` with no ``from_``
    goes out as. It is null when the workspace has several verified
    identities — then ``send_email`` rejects a missing ``from_`` and you
    must pass one from ``items``.

    Example:
        list_email_domains()

Input Schema

Name	Required	Description	Default
`limit`	No
`cursor`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.29.0Oct 21, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Annotations already mark it read-only, and the description adds the non-obvious rules: only 'verified' rows can send, custom domains are bare DNS names accepting any local-part while hail_mail domains are full addresses, and send_email rejects a missing from_ when there are multiple verified identities. These are real behavioral constraints beyond structured data.

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?

Front-loads the purpose, then the when-to-use rule, then return shape, then the domain-kind semantics and the default_from edge case. Dense but every block earns its place; the shape could be slightly tighter, but nothing is wasted.

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

Completeness4/5

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

Covers purpose, usage gating, return shape (even though an output schema exists), field semantics, and the default_from null edge case — more than enough for a read-only list tool. The only gap is pagination parameter behavior.

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

Parameters3/5

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

Schema description coverage is 0%, so the description should compensate for limit and cursor. It only touches pagination indirectly by showing next_cursor in the return shape; neither limit nor cursor semantics (page size, default, how to resume) are explained.

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?

States a specific verb and resource ('List the addresses this workspace can send email from') and scopes it to the workspace, which clearly separates it from send_email and the other listing siblings. An agent knows exactly what it will get without opening the schema.

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

Usage Guidelines5/5

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

Explicitly says to call this BEFORE send_email when the from_ address is unknown and warns 'do not guess a domain', naming both the trigger and the alternative misuse. It also states the follow-up condition (pass a from_ from items when default_from is null).

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