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

With no annotations, the description carries the burden and does disclose important behavior: fallback reporting when no block row exists, the meaning of the -1 aggregate/default row, and common TelcoData fields returned. It does not discuss auth requirements or rate limits, but the core lookup behavior is transparent.

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 front-loaded with the use case and then moves to fallback behavior and field semantics. It is reasonably efficient, though the field list and repeated aggregate explanation add some length beyond the minimum needed.

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?

There is no output schema and no annotations, but the description gives common return fields and explains the fallback-to-aggregate behavior. It is nearly complete for a read-only lookup, with only minor gaps around error and auth details already covered by the schema.

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 real-world meaning beyond the schema by explaining the seventh digit, individual pooling blocks 0-9, and the special -1 whole-prefix aggregate.

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: looking up one thousands block within an NPA-NXX. It also scopes the tool with the seventh-digit example and distinguishes the granularity from broader exchange or number lookups in the sibling set.

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 usage conditions: when the user provides the seventh digit or asks who owns/routes a specific block. It does not name alternative sibling tools or state when not to use it, so it falls short of the top score.

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