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

The annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, and the description adds substantial behavioral detail beyond them: oldest-first ordering, default batch size, the pagination loop, and response fields such as has_more, count, and next_last_received_id.

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?

The description is dense and front-loaded: it establishes the resource and ordering, then explains pagination mechanics, filters, and the endpoint without wasted text. Every sentence contributes to correct invocation.

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?

There is no output schema, so the description needed to sketch return behavior; it does so by naming has_more, count, and next_last_received_id. It does not describe the message payload fields or auth requirements, but it is otherwise sufficient for a read-only paginated fetch 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%, so the per-parameter meanings are already well documented. The description adds cross-call meaning for last_received_id, including how to use next_last_received_id and when to stop based on count, which goes beyond the schema's individual field descriptions.

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?

The description states a specific verb and resource: fetching incoming SMS received on shortcodes/numbers. It also specifies ordering and batch behavior, and 'incoming' clearly distinguishes it from the send_sms sibling without needing to name it.

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?

It gives explicit pagination usage: start with last_received_id=0, then pass next_last_received_id from the previous reply, and keep calling until count is 0. Optional shortcode and keyword filters are noted, but it does not explicitly name an alternative tool or a when-not-to-use case.

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