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

Annotations already declare readOnlyHint=true and openWorldHint=true, but the description adds genuinely useful context beyond them: it discloses that the underlying call is POST /api/RetrieveUserSettings, which stops an agent from mistaking a POST endpoint for a mutation. It also lists the concrete fields returned, which annotations cannot convey since no output schema exists.

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 resource and the returned fields, then the endpoint detail. Nothing is padded and nothing needs re-reading.

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, the description must carry the return-shape burden, and it does by naming the four meaningful values. For a zero-parameter read with annotations covering safety, an agent has everything needed to call it correctly.

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?

Zero parameters, so the baseline is 4; the empty schema means there is no parameter semantics to explain or compensate for.

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?

Uses a concrete verb ('Show') on a specific resource ('the SMS Everyone account') and enumerates exactly what is returned: user id, remaining credits, unicode flag, international-messaging flag. No sibling tool touches account-level settings, so the boundary is unambiguous without naming them.

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: an agent can infer this is a pre-flight check before sending or a credit check. There is no explicit when-to-use statement, no prerequisites, and no named alternative (none exists among siblings, which mitigates the gap only slightly).

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