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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds traits the annotations do not: a guaranteed newest-first ordering and the existence of cursor-based paging over recent receipts, which tells the agent how to walk the result set.

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?

Two sentences, no filler, with the resource and ordering front-loaded before the filtering and usage guidance. Every clause 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?

An output schema exists, so return values need no explanation, and all four parameters are fully described in the schema. With annotations covering safety, the description supplies the remaining context an agent needs to call this correctly.

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%, so the schema already documents limit, before, address, and context, giving a baseline of 3. The description restates the address filter and the receivedAt cursor but adds no format or syntax detail beyond the schema (and uses a slightly different label for the 'before' param).

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 (List), resource (received inbound email messages), scope (workspace's programmatic addresses), and ordering (newest first). This cleanly separates it from senderkit_messages_list (outbound) and senderkit_inbound_messages_get (single message) 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 two usage contexts: checking whether mail has arrived, and paging through recent receipts. Strong positive guidance, but no when-not-to-use condition or named alternative tool.

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