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

Annotations already establish a safe, idempotent read, and the description adds substantial context beyond them: it details what is returned (the word in seven toll free area codes with status and price, a recommended pick, $49 close versions, local numbers, category pages, and completion links). This pricing and output disclosure is meaningful behavioral detail.

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?

The definition is long but front-loaded: purpose first, then usage triggers, then the return payload. Each sentence carries information, though the single extended sentence listing return contents could be trimmed for readability.

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 only two well-documented params, full annotations, and an output schema, the description covers everything an agent needs: trigger conditions, exclusions, input shape, and expected output. Nothing material is missing.

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 100%, so the baseline is 3; the description adds intent and examples by naming concrete words ('PLUMBER, BAKERY') for the required word param. It also clarifies that state yields local numbers 'when one is given,' adding marginal meaning over the schema descriptions.

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?

The description states a specific verb and resource ('Find a new phone number for a business that spells a word') plus the concrete scope (toll free vs local). It also explicitly disclaims what it is not ('It doesn't look up an existing business's phone number'), which separates it from siblings like find_business_numbers and check_number.

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 gives explicit when-to-use triggers ('Use it when someone wants a memorable or vanity number, an 800 or toll free number, or a number that spells their business name') and an exclusion ('doesn't look up an existing business's phone number'). The agent has both the positive condition and the boundary against alternatives.

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