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 needs no restatement. The description's genuine addition is the disclosure that results include the caller's own access tier (full access vs free preview) and the plan required — permission-sensitive behavior an agent could not infer otherwise. It says nothing about ordering, pagination, or catalog size, so this is solid but not rich.

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?

One dense sentence plus a two-word call to action, with the catalog scope front-loaded and zero filler. The colon-list phrasing is slightly fragmentary but readable, and no sentence could be deleted without losing content.

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 no input parameters and no output schema, the description carries the burden of explaining return values and does so field by field, including the caller-specific access flag. Missing only ordering/pagination behavior, which is minor for a zero-argument catalog listing.

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, so there is nothing for the description to disambiguate; the baseline applies. The enumerated return fields (id, category, plan, description, field count, access level) describe the response rather than parameters, which is useful but belongs to a different dimension.

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 makes clear it enumerates the full Aperiodic dataset catalog (metrics and raw) and enumerates exactly what each entry carries. That is specific and distinguishable from get_data or summarize, though it never names the sibling describe_dataset, which is the nearest neighbor for per-dataset detail.

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?

'Start here' is an explicit entry-point cue telling the agent to call this before the other tools, which is real guidance rather than implied. It stops short of stating when to move on to describe_dataset or fetch, so there are no exclusions or named alternatives.

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