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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is fully covered. The description adds useful provenance ('Source: Yahoo Finance via yfinance. No API key required.'), but it is silent on the internal scoping behavior implied by wholesaler_ids and the caching behavior of source_resource_id, which materially change what data comes back.

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 what the tool returns, then when to use it, then the section enum, then the scope restriction and source. Every block is scannable. Minor waste: the section list is restated in the schema, and the source/no-API-key line is a trailing note.

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 an output schema present, return-value detail is correctly omitted, and the description covers scope, alternatives, and section selection adequately for a read-only fetch. The gap is the unexplained internal scoping/caching parameters, which an agent may otherwise ignore or misuse.

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 description enumerates the section values ('overview', 'holdings', 'sectors', 'bond_ratings', 'equity_holdings', 'all'), which is the single most decision-relevant parameter, and that is real added value. However, it says nothing about symbol, and says nothing about the fin-internal parameters (wholesaler_ids, source_resource_id, additional_display_fields) that the schema surfaces; with reported coverage at 0% the description only partially compensates.

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?

Specific verb+resource ('Fetch ETF or mutual fund specific data') with an enumerated payload (holdings, sector allocations, expense ratio, credit quality, style). It explicitly carves itself out from the sibling GetTickerInfo by stating 'Only works for ETFs and mutual funds. For stocks, use GetTickerInfo.' An agent can disambiguate without opening the schema.

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?

Contains an explicit 'Use this tool when:' block with four concrete trigger conditions (top-10 holdings, sector breakdown, bond rating distribution, fund comparison) plus an explicit exclusion routing to GetTickerInfo for stocks. This is the when-to-use / when-not-to-use pattern done fully.

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