Multi Mail

Edit a label

labels_update

DestructiveIdempotent

Rename a label, recolour it, or both. The id comes from labels_list. A new name carries the labels nested under it by / with it. An Outlook mailbox's category takes only a new colour, as Microsoft allows, and its folder only a new name, given where it is and keeping its id. A mailbox whose provider is imap renames its folder, which takes no colour, and answers the label's new id.

Input Schema

Name	Required	Description
`id`	Yes	A label id from labels_list.
`name`	No	Its new name.
`color`	No	Its new colour.
`mailbox`	Yes	The mailbox's name or its email address.

Output Schema

Name	Required	Description	Default
`id`	Yes
`name`	Yes
`type`	No
`messagesTotal`	No
`messagesUnread`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedOct 27, 2026
- changedInput schema / properties / id / pattern
```
Previous value: -"^[A-Za-z0-9_-]{1,128}$"New value: +"^[A-Za-z0-9_=-]{1,512}$"
```
- addedOutput schema / properties / messagesTotal
```
Added value: +{
+  "type": "number"
+}
```
- addedOutput schema / properties / messagesUnread
```
Added value: +{
+  "type": "number"
+}
```

Changed2 schema fields changedOct 8, 2026

changedInput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

changedOutput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Changed2 schema fields changedOct 6, 2026
- removedOutput schema / properties / type / anyOf
```
Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]
```
- addedOutput schema / properties / type / type
```
Added value: +[
+  "string",
+  "null"
+]
```
First observedOct 5, 2026

TDQS

A4.3/5.0

Behavior5/5

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

Annotations already flag destructive and idempotent behavior, but the description adds meaningful non-obvious effects: a new name carries nested labels, Outlook category/folder constraints apply, and an IMAP rename answers the label's new id. These details go well beyond what the annotations provide.

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?

The purpose is front-loaded and the provider-specific cases are packed efficiently into four sentences with little waste. The phrasing 'by / with it' is slightly awkward, and the provider detail density keeps it from being maximally crisp.

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 provider-sensitive update tool, the description covers the key cases and relies appropriately on the schema for parameter details and the output schema for return values. No major behavioral or usage omission remains.

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 schema already documents all four parameters and the colour enum. The description still adds provider-dependent meaning for name and colour, though it does not add syntax or enum details beyond the schema.

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

Purpose4/5

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

The opening sentence gives a specific verb and resource ('Rename a label, recolour it, or both') and clearly identifies an edit operation. It references labels_list as the id source but does not explicitly distinguish this tool from labels_create or labels_delete.

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 states the prerequisite that the id comes from labels_list and gives provider-specific applicability rules, such as Outlook categories taking only a new colour and Outlook folders only a new name. It does not explicitly say when not to use the tool or name create/delete as alternatives.

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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