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

Annotations already cover readOnlyHint=true, destructiveHint=false, and openWorldHint=true; the description reinforces the safety profile with 'this tool never buys a number,' which is the key behavioral risk for a number-search tool. It also discloses that results carry price, which annotations don't express.

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 what is searched and the optional filter in the first clause, then the safety constraint and the backing GraphQL query name. The GraphQL reference is minor but useful for debugging; nothing is padded.

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 compensates by noting results include price. It is a single optional parameter, read-only tool, so the remaining omission (result ordering/pagination) is small.

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 description coverage is 100% and the single parameter's pattern and description already document the prefix semantics. The description's 'optionally starting with some digits (for example an area code)' mirrors the schema rather than adding new meaning, so baseline 3 applies.

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 (phone numbers available to buy), plus scope: the account, optional prefix, and that results include pricing. No sibling tool covers number search, so no ambiguity risk.

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?

Establishes clear context: numbers that could be bought, with an optional prefix filter. It also explicitly warns this tool never buys, implicitly pointing an agent to a purchase step elsewhere. No named alternatives exist among siblings, so the bar is met without exclusions.

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