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

Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond by disclosing the response contract: `limit_applied`, the default 100 / max 1000 cap, and the crucial fact that there is NO continuation token, so `possibly_truncated: true` is the only truncation signal and a clipped series is indistinguishable from a complete one. This is exactly the non-obvious behavior an agent needs to avoid reporting partial data as full history.

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?

Front-loaded with the resource and return shape, then the truncation caveat. It is dense but nearly every clause carries distinct information; the single long paragraph slightly buries the truncation warning rather than giving it its own line.

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 return values, and it delivers: the quote fields, the metadata fields (`limit_applied`, `count`, `possibly_truncated`), and how to interpret them. Nothing an agent needs to call and correctly interpret this tool is missing.

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 83%, so the schema already documents most parameters (baseline 3). The description adds meaning beyond it by tying `limit` to the observed `limit_applied` value and to the truncation flag, and by framing `fromTimestamp`/`toTimestamp` as the manual paging mechanism in place of a cursor.

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: historical USD price series for a token contract on a chain, with the exact quote shape ({ timestamp, usd, block }). 'Historical' implicitly separates it from the getTokenPrice sibling, but the description never names that sibling or states the contrast explicitly, so an agent must infer the routing.

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?

It gives real operational guidance on what to do with a clipped result (raise `limit` or walk `fromTimestamp`/`toTimestamp`), which is actionable. However it offers no when-to-use/when-not guidance relative to getTokenPrice or other price-related siblings, so the alternative-selection dimension is missing.

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