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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds genuinely non-obvious behavioral context beyond the annotations: the list is filtered to still-pending items and excludes messages scheduled through the portal UI. It omits pagination and ordering behavior, which keeps it 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?

Two sentences, front-loaded with the scope and the exclusion caveat, plus the backing REST endpoint. No filler and nothing 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 zero-parameter read-only list tool, the description covers scope, filter semantics, and the underlying endpoint. With no output schema, it could have said a word about the shape of the returned list (e.g. recipient, scheduled time), but the omission is minor given the tool's simplicity.

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?

The tool takes zero parameters, so the schema has nothing to document and the baseline is 4. The description adds no parameter semantics because none exist.

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 SMS ... scheduled through the send API and are still waiting to go out') and pins the exact scope by excluding portal-created messages. An agent can tell instantly that this is the pending-scheduled-message lister, distinct from voodoosms_list_inbox or voodoosms_list_delivery_reports.

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?

Provides clear selection context: use it for messages scheduled via the send API, and it explicitly notes that portal Web SMS schedules are not returned. It does not, however, point to a related sibling such as voodoosms_cancel_scheduled_message as a follow-up action, so routing is clear but not fully elaborated.

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