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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds that results come back as a paginated Feed and exposes the raw endpoint, but omits richer behavior such as ordering or default page size (which the schema carries). Adequate but not rich.

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 tight sentences plus an endpoint line; the resource and scope are front-loaded with no filler. The endpoint restatement is mildly redundant but functional.

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 read-only list tool with no output schema, the description conveys the returned entity (TextNumber with TextNumberID), the Feed pagination model, and the underlying API route, which is enough to invoke it correctly. Minor gaps remain around ordering and default page behavior, but the essentials are present.

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?

All four parameters (page, pagesize, takesize, params) are fully documented in the schema at 100% coverage, so the schema does the heavy lifting. The description adds no additional parameter semantics, which is the baseline 3 case.

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 ('List the toll-free text (SMS) numbers on your account') and names the concrete return type (Feed of TextNumber objects) plus the underlying endpoint GET /v1/textnumbers. This distinguishes it clearly from siblings like list_broadcasts or list_lists.

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 hints at downstream usage by noting the TextNumberID is needed for a 1:1 conversation text and cross-references send_text_message. However, it gives no explicit when-to-use vs. when-not guidance nor compares against other list/request siblings such as textemall_request.

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