List Inboxes

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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds the return shape and the scoping intent, but discloses nothing extra about pagination behavior, default page size, or rate limits. With annotations carrying the behavioral burden, this is an adequate but not rich 3.

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?

Bold-labeled sections (Purpose, NOT for, Returns, When to use) make it scannable and the purpose is front-loaded. Slightly longer than necessary with some overlap between the Purpose and When-to-use lines, but every section earns its place.

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 compensates by enumerating every returned field (id, name, email_address, from_name, unread, last_received, created_at, updated_at). Combined with the safety annotations and 100%-covered params, an agent has everything needed to call and interpret this tool.

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 description coverage is 100% – after/before mutual exclusivity, the 404 on unknown IDs, and the 1-100 limit range are all documented in the schema itself. The description adds no parameter detail, so the baseline 3 applies.

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 ('List the Resend inboxes on the account') and distinguishes itself from the confusable siblings list-received-emails and list-emails, which also list messages. An agent can route to this tool without opening any schema.

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 names the conditions to use it ('what inboxes do I have?', need an inbox ID) and the conditions NOT to use it, routing to named alternatives for each exclusion. Nothing is left to inference.

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