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

The description adds substantial behavioral context beyond the annotations: balance is reserved up front, the job runs in the background, a customer API key is required, and the job bills the account that owns the key. These side effects are critical for a non-read-only tool, and the description discloses them clearly.

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 description is compact and front-loaded: it opens with the core action and constraints, then covers billing, background execution, and monitoring in two tight sentences. There is no redundant or vague filler.

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 two-parameter tool with an output schema and useful annotations, the description covers all key operational concerns: async behavior, size limit, balance reservation, status checking, authentication, and billing. Nothing essential for an agent to select and invoke the tool correctly 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?

The input schema already documents both parameters completely, including the phone number format, maxItems, and the products default. The description restates the geography and size limit but does not add meaningful parameter-level meaning beyond 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?

The description states a specific action, submit, and a specific resource, an ASYNC bulk lookup job, with explicit scope of up to 10000 North American phone numbers. The ASYNC qualifier and the pointer to vri_bulk_status help position it among sibling lookup and status tools.

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 description clearly frames when to use the tool: for large bulk asynchronous lookups, with balance reserved up front and progress tracked via vri_bulk_status. It does not explicitly contrast this with synchronous alternatives like vri_number_lookup or vri_bulk_lookup, but the async context is clear enough for an agent to infer the right scenario.

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