Update Inbox Label

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

Annotations establish that this is a non-read-only, non-destructive, closed-world mutation. The description adds genuinely useful behavior beyond that: the change propagates to every thread already carrying the label, and the new name must be case-insensitively unique on the inbox. It stops short of describing failure behavior or return values, but the side-effect disclosure is valuable.

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?

Five short sentences, each carrying distinct information: purpose, optionality rule, propagation effect, validation rule, and ID lookup. The purpose and the mutation constraint are front-loaded with 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?

With no output schema, the description carries the explanatory load and does so well for a 4-parameter mutation: it covers optionality, side effects, and name validation. It could go slightly further on what happens when the uniqueness rule is violated, but nothing critical is missing for correct invocation.

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 two rules the schema does not encode: the at-least-one-of-name/color requirement (the schema only marks inboxId and labelId required) and the case-insensitive uniqueness constraint on name.

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+resource (update a label in a Resend inbox) and enumerates the exact operations (rename, recolor, or both), which cleanly separates it from create-inbox-label, list-inbox-labels, and remove-inbox-label.

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?

Gives a hard usage constraint ('At least one of the two is required') and routes the agent to list-inbox-labels to obtain the labelId. It does not explicitly contrast when-to-use against the sibling label tools, but the scope is clear enough to act on.

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