Create or update a tag

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

Discloses color format (#RRGGBB) and behavior regarding key usage. Annotations indicate idempotent and non-destructive nature, which description does not contradict. No mention of side effects or permissions.

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

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

Extremely concise; two sentences plus code block. Front-loaded with purpose, no filler. Every sentence adds value.

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

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

For a 4-parameter tool with output schema, description covers creation vs update and color format but omits explanation of 'confirm' and potential side effects. Output schema exists, so return values need not be explained.

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

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

Description explains 'key' (omit/create vs pass/update) and 'color' (format) but does not describe 'label' or 'confirm'. With 0% schema coverage, description compensates partially.

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

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

Title and description clearly state the tool creates or updates a tag. It distinguishes from siblings like mail_tags (list) and mail_tag_delete (delete).

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

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

Explicitly instructs to omit 'key' for creation and pass an existing key for update, providing clear usage guidance. Lacks explicit when-not-to-use, but sufficient for the role.

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