Get Inbox

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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered. The description adds value by enumerating the returned fields, which is the only place that information exists since there is no output schema. It does not mention error behavior for a missing ID, so it stops short of a 5.

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?

Front-loaded with the resource and its returned fields, followed by the resolution path and the handoff to sibling tools. The return-field list is long but justified by the absence of an output schema; no sentence 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 single-parameter read tool with no output schema, the description supplies the return shape, the accepted input forms, and the surrounding workflow. Nothing an agent needs in order to call this correctly is missing.

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% and already documents that inboxId accepts an ID or email address (not the Resend receiving address), so the baseline is 3. The description adds actionable semantics beyond the schema by telling the agent it can pass a user-supplied address directly without a lookup first, which changes how the parameter is sourced.

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 (get) and resource (inbox) and enumerates what the result contains: domain, receiving address, creation time, unread thread count, draft count, last-received time. An agent can distinguish it from list-inboxes and from thread/draft tools in the same family without opening the 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 routes the agent: if the user names the address, pass it directly; otherwise use list-inboxes to resolve the ID. It also states the downstream step ('Use the returned ID with the other inbox tools'), covering when and how this tool fits into a workflow.

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