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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds useful context beyond them: chronological ordering (oldest day first), the earliest available date, and the informational-only disclaimer. It omits pagination/truncation behavior for the 365-day ceiling, which is a minor gap.

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 core statement, then a field inventory and two short qualifying sentences; no wasted framing. The middle field list is dense (AUM, premium to NAV, streak) but each item tells the agent what it can retrieve, which is justified when no output schema exists.

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 burden of describing returns, and it largely does by enumerating the per-day fields, ordering, and history start date. It leaves the relationship to get_zec_etf_signal unexplained and doesn't describe behavior at the start-of-history boundary (e.g. fewer than `days` results).

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 description coverage is 100%, so all three parameters are already documented in the schema. The description restates the two optional flags ('adds each day's component scores and rationale') without adding format or performance nuance, and says nothing about the `days` window beyond what the schema states. 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?

States a specific resource and shape: 'Daily history of the ZEC ETF flows indicator, oldest day first', then enumerates the returned fields. The word 'history' implicitly separates it from get_zec_etf_signal (current signal), but no sibling is named explicitly, so the differentiation is inferred rather than stated.

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?

The description gives a hard boundary ('History starts on 2026-09-07') and explains what the optional flags add, which helps an agent decide how to call it. It never says when to prefer this over get_zec_etf_signal or get_crypto_prices, so routing guidance is only implied by the word 'history'.

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