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

Annotations already establish readOnlyHint=true (safe read) and openWorldHint=false (closed dataset), so the safety profile is covered. The description goes beyond that by disclosing what the response contains (per-registry/per-layer age, promised freshness in hours, in/out of promise) and by asserting the tool is intentionally distinct from service health. No rate limits or failure behavior are mentioned.

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?

Four short sentences, front-loaded with the imperative use case, followed by output contents, a disambiguating contrast, and a next-step pointer. No sentence is filler and nothing important is buried.

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?

With zero parameters, no output schema, and a low-complexity read, the description covers what the agent needs: when to call it, what it returns at a field level, and where to go next. A brief note on tolerance thresholds or how 'inside the promise' is judged would make it fully self-contained.

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 no parameters and the schema is empty, so the baseline of 4 applies. There is no parameter syntax the description could usefully add.

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?

Specific verb+resource ('CHECK HOW CURRENT THE DATA IS') plus concrete scope: 'Lists every trial registry and content layer with the age of its data, its published freshness promise in hours and whether it is inside that promise right now.' It also draws an explicit boundary against a related concept ('up is not the same as current'), so the agent can separate it from health/status style siblings.

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?

Explicit trigger: 'CHECK HOW CURRENT THE DATA IS before you build on it,' and it rules out conflating it with service health. It hands off to a named sibling ('NEXT: get_registry_sources for full provenance'). What's missing is any statement of when this check is unnecessary, so it stops short of the 5 level.

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