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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, so the safety profile is covered. The description adds valuable behavioral context: it lists the specific evidence categories, states that each is dated with its source, and crucially interprets an empty result ('empty means DFX observed no change, not that nothing is happening'). This goes beyond the annotations.

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 sentences, front-loaded with the purpose and evidence types, then a crucial clarification about empty results. No wasted words, perfectly sized for the tool's simplicity.

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 simple read tool with two parameters and no output schema, the description covers the key points: what it returns (types of evidence, each dated with source), how to interpret empty output, and implicitly the dfx_id parameter. It does not specify the return format in detail, but that is acceptable given the absence of an output schema and the tool's simplicity.

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 only 50%: dfx_id is described with its ID format, but within_days is not described at all (only has a default). The tool description references a 'window' but does not connect it to the within_days parameter, nor does it explain semantics like the default 180 days. The description does not compensate for the missing schema documentation.

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's purpose: to return evidence-backed reasons an entity is relevant now, listing specific event types. It distinguishes itself from generic get_entity or search_events by specifying the nature of the output. However, it does not explicitly name any sibling alternative, which would push it to 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 clear context: use this to understand why an entity matters now, with a list of event types. It also clarifies the meaning of an empty result. However, it does not explicitly state when NOT to use it or point to alternative tools like changes_since or search_events, leaving some ambiguity for an agent.

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