List recent messages

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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive behavior. The description adds useful behavior beyond annotations: newest-first ordering and pagination via the returned next_cursor. It does not mention default limit or response shape, but the safety profile is already covered by annotations.

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 with no filler: the core action and ordering are front-loaded, followed by the essential pagination instruction. It does not repeat schema details or annotations.

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 list tool with five optional parameters and no output schema, the description covers the essential calling contract: ordering, filters, and pagination. It could be more explicit about default limit and returned message fields, but the core information needed to invoke it correctly is present.

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 0%, so the description must compensate. It maps status, tag, and recipient to the schema's status, tag, and to parameters, and it references cursor pagination. However, it does not explain limit semantics, cursor mechanics beyond 'returned next_cursor', or the fact that all parameters are optional.

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?

Description states a specific verb and resource ('List messages') with ordering ('newest first') and filter dimensions (status, tag, recipient). It is clearly distinct from sibling get_message (single message) and list_bounces (bounces), so an agent can select it 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?

The description gives clear context: use this when you need a paginated list of messages filtered by status/tag/recipient. It does not explicitly name alternatives or exclusion criteria, but the collection-vs-single and messages-vs-bounces distinctions are implied by the wording.

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