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

Annotations already declare readOnlyHint, idempotentHint and closed-world, so the safety profile is covered. The description adds real substance beyond that: the 7-day staleness threshold used for is_stale, the UTC basis for the age, the fact that refresh mechanics are reported, and a concrete example output where no output schema exists. Response shape is disclosed via example rather than a schema, which is slightly less precise but still useful.

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 return fields are front-loaded and the example output plus the closing usage cue are compact. The opening sentence is a long list that reads as a run-on, but every clause names a distinct returned value, so little is wasted.

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?

There is no output schema, so the description carries the full burden of explaining returns, and it does: it enumerates each reported field, gives a worked example object, and states the staleness rule. Combined with annotations covering safety and idempotency, an agent has everything needed to call and interpret this tool.

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 are zero parameters and the description states "No arguments." explicitly, removing any doubt about required input. With no parameters to document, the baseline of 4 applies and nothing is left ambiguous.

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 and resource: it returns the snapshot date, its age in days, a staleness flag, the newest server first-publish date, the newest spec change date, and how data is refreshed. That is far more concrete than a restated title. It does not, however, distinguish itself from the sibling snapshot_info, which an agent could easily confuse with this tool.

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?

"Good for 'How fresh is this data?'" implies the triggering question, which is genuine usage guidance. But there are no when-not conditions and no named alternatives, even though snapshot_info sits among the siblings and plausibly overlaps. The agent has to infer the boundary itself.

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