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

Annotations already declare a safe, idempotent read, so the description correctly spends its words elsewhere: it discloses the quarterly cadence, that values are never interpolated, that each snapshot is exactly one point, and that CC BY 4.0 attribution is required. Those are non-obvious traits an agent could not infer from the schema or 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?

Three short sentences with little waste, but the lead sentence is a verbless fragment ('Quarterly snapshots of the same aggregates...') that delays comprehension. The license clause is relevant but competes with the missing core statement of what the tool returns.

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 output schema, the description must carry return-shape information. It conveys the point-per-snapshot structure and per-chart series, but omits how far back the history goes, ordering, or the response container, leaving the agent to guess at the data's extent.

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 coverage is 100%: the single `chart` enum parameter is already documented as 'One chart slug; omit for every series.' The description's 'one series per chart across snapshots' adds only marginal framing about how the parameter shapes output, so the baseline 3 applies.

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 indicates the resource is historical quarterly snapshots of the same aggregates as `get_stats`, but it is a noun phrase with no verb and never says it 'returns' or 'retrieves' anything. The reference to 'the same aggregates' only differentiates it from `get_stats` if the agent already knows what `get_stats` does.

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?

There is no explicit statement of when to call this instead of `get_stats` or the other siblings; the link to `get_stats` is implied through 'the same aggregates' rather than stated as an alternative. No prerequisites or exclusions are given.

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