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

readOnlyHint already declares this as a safe read, so the bar is lower; the description adds genuinely useful behavioral context by disclosing that the call is free and consumes no credits, plus the underlying REST route. It does not disclose behavior for edge cases such as a report that is not yet ready or an invalid request_id.

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?

Two compact sentences, front-loaded with the purpose and the cost fact, with the REST endpoint appended as secondary reference. Nothing is redundant or 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?

There is no output schema, so the description carries the burden of describing what a 'lookup report' contains (e.g., carrier/network, ported status, timestamps) and what a not-yet-complete report looks like. It explains how to obtain the input but not what comes back, leaving a notable gap for the only retrieval tool in the group.

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 request_id parameter is already documented as coming from d7_lookup_number, so the description adds no format or constraint detail beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 and resource ('Read the stored result of an earlier number lookup by its request_id') and the retrieval-by-key relationship implicitly separates it from d7_lookup_number, which initiates the lookup. An agent can distinguish this from every sibling without opening the 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?

Establishes clear context: this is the follow-up read step for a lookup previously started, keyed by the id that d7_lookup_number returned. It does not name an explicit alternative or state exclusions (e.g., what to do if no lookup was performed), so it stops short of full when/when-not guidance.

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