Get ETF time series

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so 'Read-only' adds little. The real value is the disclosure that unavailable series are surfaced as named gaps and never approximated with price returns — a non-obvious behavioral contract an agent could otherwise get wrong.

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?

Two tight sentences: the primary capability is front-loaded and the availability caveat follows immediately. No filler, and 'Read-only' is the only arguable redundancy.

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?

An output schema exists, so return shape needs no explanation, and the description covers the subtle part — partial series availability. For a 7-parameter tool it omits any note on how `limit` interacts with date filtering and interval aggregation, which is a modest but real gap.

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 57%, so the schema carries much of the burden. The description adds meaning for `series` (unsupported stored series -> unavailableSeries) and for `benchmarkTicker` (an explicit ticker is required because a benchmark name cannot resolve a price series safely), but says nothing about `limit`, `startDate`, or `endDate` beyond what the schema shows.

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 ('Fetch ETF price or price-return history') plus the interval granularity, so an agent knows exactly what it retrieves. It does not name a sibling to distinguish itself from, e.g., get_stock_price_history or get_etf_snapshot, leaving that separation implicit in the 'ETF' qualifier.

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?

Conveys conditional availability ('returned only when their required source data ... exists') and the fallback policy, which is genuine usage context. However, it never says when to prefer this over get_stock_price_history, get_etf_snapshot, or get_etf_fund, and gives no guidance on choosing intervals or date windows.

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