Update Inbox

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

Annotations already declare the safety profile (readOnly=false, destructive=false, openWorld=false), so the bar is lower. The description adds two pieces of behavior the annotations cannot convey: the inbox email address is immutable, and at least one mutable field must be supplied. It stops short of describing error modes or response shape.

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?

Three tight sentences, front-loaded with the action and scope, followed by the two field meanings and the constraint. Every sentence carries load and nothing is redundant.

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 3-parameter mutation tool with full schema coverage and no output schema, the description covers what changes, which field combination is legal, and what cannot change. Missing only permission/auth requirements and error behavior, which is a minor gap given the annotations cover safety.

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; the description earns an extra point by stating the cross-parameter constraint ('at least one of the two is required') that the schema does not encode with anyOf/oneOf, plus the immutability rule for the inbox address. It does not add syntax or format detail beyond what the schema already documents.

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 an inbox in Resend') and enumerates exactly which fields can change: the internal name, the outbound display name, or both. It distinguishes the operation's scope well, but never names or contrasts with the closely-related siblings (update-inbox-thread, update-inbox-agent), which the agent must disambiguate from the namespace alone.

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 description supplies one real precondition -- 'At least one of the two is required' -- which is genuine when-to-use information. However, it gives no guidance on when to prefer this over update-inbox-thread, update-inbox-agent, or update-domain, so the usage signal is implied rather than explicit.

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