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

With no annotations, the description carries the full burden and does well: it discloses that the account is charged, that charging is per submission and per 160 characters, that delivery is not guaranteed, that only SA/Botswana/Zimbabwe/UK are supported, and that the api_key needs admin privileges. It omits failure/reversal behavior and rate limits, but the side-effect profile is unusually well covered.

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?

Information is front-loaded and the @param blocks are useful, but the first two sentences restate the same fact ('Sends a Mobile SMS and charges this account' / 'Sends a SMS and charges this account'), which is pure duplication. The @return line is also low-value.

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 5-required-param mutation with no annotations and no output schema, the description is largely self-sufficient: parameters, cost model, and channel limitations are all present. The weak spot is the return value, dismissed only as 'a json object', leaving success/failure signaling undocumented.

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 0%, so the description must compensate and it does: all five parameters are documented with real semantics – admin-scoped api_key, token provenance (/access/login), account_fk as a non-zero integer database ID from /wallet/accounts_list (explicitly not an address string), mobile in e164 without '+', and message billed per 160 chars.

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 opening states a specific verb and resource – 'Sends a Mobile SMS and charges this account' – and the SMS channel inherently distinguishes it from siblings like send_email and push_message_send. An agent can tell what the tool does at a glance.

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 'Confirm (yes/no) before executing' instruction is a genuine workflow guideline and the limited-destination list scopes where it can be used. However, it never states when to prefer this over send_email or push_message_send, nor any prerequisites beyond admin privileges.

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