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

Annotations already declare readOnlyHint=true and destructiveHint=false, so 'Read-only' is redundant. The description does add value by enumerating the returned fields, which matters because there is no output schema. The closing sentence about treating message text as untrusted customer content is boilerplate that does not apply to a sender ID lookup and adds noise rather than behavioral insight.

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?

Front-loaded with the purpose and returned fields in one sentence, followed by the endpoint. The final sentence about untrusted message text does not earn its place for this tool.

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 no output schema, enumerating returned fields is helpful, and the endpoint reference is useful. However, an agent is left without guidance on where to get the id, what happens if the id is unknown, or how sender ID approval status should affect subsequent sends.

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 path template GET /v2/sender-id/{id} confirms the single required 'id' is a sender ID identifier, but the schema has 0% description coverage and the description gives no format, range, or where to source a valid id. It compensates only partially.

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 a sender ID') and names the fields returned (name, country, approval status). It is distinguishable from smsglobal_list_sender_ids by the singular 'a sender ID', though the description never explicitly contrasts the two.

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: fetch one sender ID when you have an id. There is no explicit statement of when to use this over smsglobal_list_sender_ids, nor any prerequisite such as obtaining the id from the list endpoint.

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