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

Annotations already cover the safety profile (readOnlyHint, openWorldHint, destructiveHint false), so the description's real contribution is the caveat that delivery states are 'observations, not a guarantee of receipt' and the security instruction to treat message text as untrusted customer content. Those are genuine, non-obvious behavioral facts an agent would otherwise miss.

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?

Three short sentences plus the endpoint, all front-loaded with no filler; each clause adds a distinct fact (content, delivery caveat, safety warning). The telegraphic style is slightly choppy but nothing is wasted.

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 one-parameter read with no output schema, the description does the necessary work: it names what comes back (parts, body, destination, delivery state) and flags the delivery-state semantics. Only the id format ambiguity remains unresolved.

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 single `id` parameter has 0% schema description coverage, so the description must carry the semantics. It partially does via 'GET /v2/sms/{id}', implying a message identifier, but it never says whether this is the numeric internal ID or the provider's message reference, nor what happens for an unknown id.

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 ('Read outgoing message parts, body, destination and delivery state') and pins the endpoint ('GET /v2/sms/{id}'), which makes clear this is a single-message fetch. It doesn't explicitly contrast itself with smsglobal_list_outgoing_messages, though the singular/ID-based framing implies the distinction.

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?

Usage is only implied: the {id} path parameter signals 'call this when you already have a message id,' but there is no statement of when to prefer this over list_outgoing_messages or how to obtain an id. No exclusions or prerequisites are given.

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