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

Annotations already declare openWorldHint=false, idempotentHint=true and, notably, destructiveHint=true, so the agent knows the operation mutates state. The description adds genuine value with the partial-update rule ('Send only the fields that should change'), but it never addresses the destructive hint it is paired with — that renaming overwrites the prior name and could break anything referencing that tag, and there is no note on failure modes such as duplicate names.

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?

One lead sentence up front with scope and target fields, then a short bulleted trigger list, then a single constraint sentence. No filler, and the most important fact (what the tool mutates) is first.

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?

With an output schema present the description needn't explain return values, and three flat parameters keep the surface small. The remaining gap is behavioral rather than structural: no guidance on where tag_uuid comes from or what happens when a supplied name collides with an existing tag.

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?

Schema coverage is 100%, so the baseline would be 3, but the description adds semantics the schema does not: it flags tag_uuid as the required anchor and states that unspecified fields are left untouched, clarifying partial-update behavior rather than full replacement.

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?

States a specific verb and resource ('Update an existing tag') and names the only two mutable fields (name and color), which cleanly separates it from create-account-tag and delete-account-tag in the sibling list. It never names a sibling explicitly, but the update-vs-create-vs-delete boundary is unambiguous.

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?

The 'Use this tool when' bullets give concrete triggering conditions (rename a tag, change a tag's color), which is more than most sibling tools provide. It stops short of exclusions — nothing says to use list-account-tags to discover a tag_uuid, or that this is not the tool for tagging documents (update-document-tags).

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