Get ETF fund by ISIN

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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the closing 'Read-only' adds nothing. The description does add real context beyond annotations: it enumerates the returned categories and specifies that ratios are in percentage points, which prevents unit misinterpretation.

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?

Four short sentences, front-loaded with the fund-vs-listing distinction and then the return shape, then use cases, then the unit caveat. The final 'Read-only' sentence is redundant with annotations and could be dropped.

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 values needn't be detailed, yet the description usefully sketches the result categories and unit convention. With annotations covering safety and a zero-required-param schema, an agent has everything needed to call it correctly.

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 both params (isin, ticker) are already fully documented with examples, and the description's '(or any venue ticker of the fund)' largely repeats the ticker schema text. It adds only the implicit either/or framing, which the schema already conveys with 'Provide this or isin'.

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: given an ISIN or venue ticker it returns the fund's identity, costs, index, distribution policy, wrapper and all listings. The opening line 'Resolve one FUND rather than one listing' explicitly separates it from listing-level siblings like get_etf_snapshot or the ticker-oriented tools.

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?

Gives three concrete triggering situations (user quotes an ISIN, asks which ticker to buy on their exchange, several tickers may be the same fund), which is stronger than typical. It doesn't name a specific alternative for those cases (e.g. search_etfs for discovery), so routing coverage is clear but not exhaustive.

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