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

Annotations already declare readOnly/idempotent/no-destructive, so the safety profile is covered; the description goes further by disclosing downsampling semantics ('never a tail slice'), that first/last points are always retained, the pro-forma pre-inception behavior, and that empty series carry an explanatory note. It also confirms 'Read-only, no auth' beyond the raw hints.

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 lead sentence front-loads the core behavior and is information-dense with no filler, but the paragraph is long and crams per-asset-class spacing details (AIB, MA-RIPPLE, FTA-CRYPTOS) into a single run-on flow, making it heavier than necessary.

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 carries the return-format burden and does so: it gives the point shape ([{t, v}]), guarantees the first/last inclusion, and explains the empty-series note. Nothing an agent needs to interpret results 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 100%, so the baseline is 3; the description adds interpretive meaning by explaining that points is a target count with first/last always kept and that the series is evenly downsampled to fit. It also references inception_at and pre_inception_points, which are not present in the input schema, adding conceptual value but also ambiguity about how they are supplied.

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?

States a specific verb and resource ('Index history for one fund') plus the exact return shape ([{t, v}] points). It explicitly contrasts with the sibling get_fund (points[0].v matches get_fund's inception_index_price_usd), so an agent can distinguish them without opening schemas.

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?

Names the alternative and the condition that selects it: 'FTA-STOCKS and EVENT-CARD have no history series — use get_fund for their current numbers.' It also explains the conditional inception_at path and what an empty series means, covering when the tool applies and when it doesn't.

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