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

The annotation readOnlyHint: true is consistent with the description's "Read-only" statement, so no contradiction. The description adds value beyond annotations by clarifying the fund-vs-listing scope, the ability to resolve from a ticker to its ISIN, and that ratios are in percentage points. This provides useful behavioral context not present in the annotations.

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 description is three sentences, front-loaded with the core concept "Resolve one FUND rather than one listing." Every sentence adds value: scope, return fields, use cases, and unit clarification. No redundant or filler content.

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?

For a moderate-complexity tool with an output schema and readOnly annotation, the description covers the essential context: the fund-level scope, input flexibility via ISIN or ticker, key returned fields, use cases, and a unit caveat. It is complete without needing to explain the output schema details, which are already structured.

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?

Both parameters have detailed descriptions in the input schema (including examples and the note to provide either isin or ticker), so schema coverage is 100%. The tool description adds little parameter-specific meaning beyond reinforcing the either-or relationship. Baseline of 3 is appropriate because the schema already carries the semantic weight.

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 description clearly states the tool resolves a FUND rather than a listing, and enumerates the returned data (identity, costs, index, distribution policy, wrapper type, and venues). It distinguishes itself from listing-specific siblings like get_etf_snapshot by the "rather than one listing" contrast, making the purpose unmistakable.

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?

Explicit use cases are given: when the user quotes an ISIN, asks which ticker to buy, or when multiple tickers may share the same underlying fund. It does not explicitly name alternative tools or state when not to use it, but the context is clear enough to guide selection among siblings.

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