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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and openWorld, so the safety profile is fully covered and the description need not repeat it. It adds only that the response is a "quick verdict" with four specific fields — helpful framing, but nothing on latency, rate limits, or what a missing/sparse report count means.

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?

One front-loaded clause with zero filler, and the returned fields are listed immediately after the use case. It is a fragment rather than a sentence, which is efficient but leaves the tool without an explicit statement of what action it performs.

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?

The tool is simple, the output schema documents return values, and annotations carry the safety profile, so this is close to adequate. What is missing is any hint about result interpretation (trust-score scale, what a low report count means) or geographic limitation guidance beyond the schema's "Danish" note.

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?

There is a single required parameter at 100% schema coverage, with the schema already stating "Danish number, 8 digits." The description adds no constraint, format, or normalization guidance beyond that, so the schema does all the work — baseline 3.

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 names the resource (an incoming phone number) and the exact payload of the result: spam level, trust score, category, report count. That field list implicitly separates it from a general phone_lookup, but no sibling is named outright, so it falls short of a 5.

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?

"For an incoming call" implies the real-time screening use case, which is genuine usage context. However, there is no explicit when-not guidance and no reference to phone_lookup for cases needing fuller detail — the agent must infer the split from the sibling's name alone.

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