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

Annotations already declare readOnlyHint=true, and the description adds key behavioral context: it 'Measures reporting activity, not phenomenon validity' and notes 'Updates: weekly.' These go beyond the annotations by warning against misinterpretation and indicating data freshness. No contradiction exists.

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 a single dense sentence of about 58 words. It packs return fields, use cases, a caveat, and update frequency without wasted words. It is not as cleanly segmented as a two-sentence structure, but it remains appropriately sized and front-loaded with the return value.

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 description lists the return fields (score, velocity_7d/30d/90d, state_leaderboard, top_shapes), data source (143k+ NUFORC/MUFON reports), update cadence, and a critical interpretation caveat. With no output schema, this provides a solid understanding. It does not specify pagination or exact data types, but for a simple read-only indicator, it is sufficiently complete.

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 one optional parameter (days) with a detailed schema description covering behavior and Gold tier requirement. Since schema coverage is 100%, the description does not need to compensate. It adds no additional parameter semantics beyond the schema, so a baseline 3 is appropriate.

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 clearly states the tool 'Returns a 0-100 US UFO/UAP sighting-report momentum index' and lists the key contents (score, velocity_7d/30d/90d, state_leaderboard, top_shapes). It uses a specific verb and resource, but does not explicitly distinguish itself from the many sibling adw tools, 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?

The description provides explicit usage context: 'Call when the user asks whether UFO sighting activity is heating up or cooling off and which states drive it, or when timing UAP-themed content, merchandise, or coverage.' It does not mention when not to use it or name alternative tools, so it lacks the full exclusion guidance for a 5.

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