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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description still adds real behavior: default descending date sort, an implicit 30-day lookback window, and the pagination cursor convention, which is exactly the kind of context not present in the 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?

Four tight sentences with no filler: identity and return fields first, then default window, then filters, then paging. Every sentence carries distinct operational information, and the API route is tucked at the end where it belongs.

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?

With 9 optional parameters, no output schema, and a read-only annotation set, the description covers the lookback window, sorting default, filter dimensions, and pagination — enough to call it correctly. Missing only edge details such as how many records a reasonable page size is or any rate-limit/auth expectations.

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 baseline is 3, but the description adds meaning beyond the schema by grouping filters ('by status, numbers, or a message id in search') and by revealing that the response carries a next_skip value to feed back into skip. The from_date default it cites is largely a restatement of the schema.

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?

It states a specific verb and resource ('List SMS messages sent from the account') plus the returned fields (recipient, status, cost) and even the backing endpoint (GET /sms/send). The list/get distinction from siblings like notifyre_get_sent_sms is only implied by scope, not named, so it falls short of full sibling differentiation.

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 clear invocation context: the default 30-day window when from_date is omitted, the filterable dimensions (status, numbers, message id in search), and the paging convention (skip = next_skip). It never says when to prefer notifyre_get_sent_sms for a single message instead, so there is no explicit exclusion guidance.

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