Search numbers to buy

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

Annotations already declare readOnlyHint and openWorldHint, but the description adds genuinely new behavioral context: pagination is stateless and must be re-passed on every call, with nothing persisted between calls. This is exactly the kind of operational detail annotations cannot convey. 'Read-only' merely restates the annotation, but the pagination disclosure carries the score.

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-loads purpose, then filters, then pagination semantics in four tight sentences with no filler. The trailing 'Read-only' is mildly redundant against the annotation, but overall sizing is appropriate for a 6-param search 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?

For a read-only search tool with no output schema, the description covers inventory scope, the fee content, all meaningful filters and pagination behavior. It does not explain result ordering or result-set size limits, which is a small remaining gap.

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 coverage is only 33%, so the description must compensate, and it does: it enumerates country (with example IN), region, contains (digits) and series (Indian series after +91), and explains the pagination params. It even surfaces a limit/offset alternative not present in the schema. Minor gap: page/per_page bounds are left to the schema.

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 (Search) and resource (Vobiz inventory of numbers available to buy) and even notes the fee information returned. It is clearly distinguishable from sibling buy_phone_number (purchase) and list_phone_numbers (owned numbers) without opening either schema.

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 phrase 'available to buy' implies this is the discovery step preceding buy_phone_number, so usage is implied, but no explicit when/when-not guidance or named alternative is given. The agent must infer the search-then-purchase flow rather than being routed to it.

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