Update Inbox Label

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

Annotations only establish readOnlyHint=false and destructiveHint=false. The description adds genuinely valuable behavior the annotations cannot convey: the change propagates to every thread already carrying the label, and a new name must not collide with another label's name case-insensitively.

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?

Four short sentences, each carrying distinct information (scope, propagation effect, rename constraint, ID source), with the core action front-loaded and no filler.

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 mutating tool with no output schema, the description covers scope, side effects, preconditions, and ID sourcing. A minor gap remains around failure behavior when the name collides (error) and whether partial updates are atomic.

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 is 3, but the description adds meaning beyond the schema: it explains that name and color are independently optional ('or both') and states the case-insensitive uniqueness rule for name, which is not encoded in the schema.

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 (update) plus resource (label in a Resend inbox) and enumerates the mutation surface (rename, recolor, or both). This clearly distinguishes it from list-inbox-labels, create-inbox-label, and remove-inbox-label in the sibling set.

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?

Explains the context of use: modify an existing label's name and/or color, with the uniqueness precondition for renaming and a pointer to list-inbox-labels for the ID. It does not explicitly state when to reach for this versus create/remove, but the intent is unambiguous.

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