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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety and data-source locality are covered. The description adds that results reflect 'right now' state and the inclusion criterion (agent blocked OR service broken), but says nothing about snapshot freshness, how often it updates, or result shape.

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?

A single sentence that front-loads the resource and scope, with the usage rationale as a compact trailing clause. No wasted wording.

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 zero-parameter, read-only list tool with no output schema, the description conveys what is returned in domain terms (roads, with the reason for inclusion). It would be slightly stronger if it hinted at the result fields or the freshness of 'currently'.

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?

The tool takes zero parameters, so there is no parameter semantics to explain and the baseline of 4 applies. The description correctly implies the call is unfiltered and takes no arguments.

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 ('List') and a precisely scoped resource ('roads where agents are currently blocked or the service is broken'), which is far clearer than the opaque tool name 'red_lights'. It does not, however, explicitly contrast itself with siblings like check_road or list_watches, so the agent must infer the boundary.

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 trailing clause 'so you can plan around them' implies the situational use case (pre-planning around outages), which is helpful context. It stops short of stating when to prefer this over check_road for a single road, or any exclusions.

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