Mailbox MCP

List send-as addresses

list_identities

Read-onlyIdempotent

List the addresses this mailbox can send as, and which one is used by default. Pass one of them as from on send_email, reply_email, forward_email or draft_email to send as that address instead of the default. Addresses are added by the mailbox owner in their account, not through this connector, and the mail server still decides whether it will carry one.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`routine`	No	The routine id written in a scheduled routine's instructions, when this call is that routine's first step. It is recorded in the mailbox's activity log with the call.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 2, 2026

addedInput schema / properties / routine

Added value: +{
+  "description": "The routine id written in a scheduled routine's instructions, when this call is that routine's first step. It is recorded in the mailbox's activity log with the call.",
+  "maxLength": 100,
+  "type": "string"
+}

First observedSep 5, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint and non-open-world, so the safety profile is covered. The description adds genuinely new behavioral context: addresses are provisioned by the mailbox owner outside this connector, and the mail server may still refuse to send as one. What it doesn't clarify is the shape of the returned list (e.g. whether the default is flagged), but the annotations carry most of the burden.

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

Conciseness5/5

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

Three sentences, front-loaded with the result and then the actionable follow-up and the caveat. Every sentence carries distinct information; no repetition of the title or annotations.

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 simple read-only listing tool with no output schema, the description covers what is returned (addresses plus the default) and the downstream usage and provisioning caveats. Nothing needed to call or interpret it is missing.

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?

One optional parameter (`routine`) with 100% schema description coverage, so the schema fully documents it. The description says nothing about `routine`, adding no meaning beyond the schema; baseline 3 applies.

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 mailbox can send as') plus the default-selection detail, which no sibling covers. An agent can distinguish this from list_mailboxes or find_contact immediately.

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 tells the agent what to do with the result — pass an address as `from` on send_email, reply_email, forward_email or draft_email — naming the exact sibling tools and the condition for using them. It also pre-empts a mistaken expectation by noting addresses are not created through this connector.

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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