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

Annotations already cover read-only, idempotent, non-destructive, closed-world behavior, and the description still adds substantial context the annotations cannot: per-number source and as-of provenance, closed-fund behavior (returns 'closed' with the day and the page's wording), and former-ticker redirection that resolves to the current fund and says so. These are exactly the edge cases an agent needs before calling.

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 scope statement is front-loaded and no sentence is pure filler — each one adds contents, edge-case behavior, or disambiguation. The benchmark sentence is dense and parenthetically overloaded, slowing parsing for a one-parameter tool.

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 does the work of describing return contents, provenance, and error-adjacent cases (closed funds, former tickers), and annotations cover the safety profile. The remaining gap is the unknown/invalid ticker case, which is left unstated alongside the closed-fund behavior.

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?

The single ticker parameter has 0% schema description coverage, so the description has to carry meaning — and it does add one important semantic: a former ticker is accepted and resolves to the fund it trades as now. It omits format specifics (casing, symbol conventions) and what an entirely unknown ticker returns, keeping it below a 5.

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 opening clause 'Everything ETFIQ publishes about one fund' gives a specific resource and scope, and the description enumerates the contents (issuer, category, sourced numbers with as-of dates, verdict, benchmark windows). It does not, however, distinguish itself from near-superset siblings such as etf_scorecard, etf_promise, or etf_benchmark, which are arguably slices of this same data.

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?

Usage is only implied: 'everything about one fund' suggests reaching for this when you need the whole picture rather than a slice. The one explicit disambiguation — that list_benchmarks covers ETFIQ's model-portfolio benchmarks, a different thing — is limited to a niche case and says nothing about when to prefer etf_scorecard or etf_promise instead.

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