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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is established and the description adds beyond it: the data source ('Yahoo Finance via yfinance'), the auth requirement ('No API key required'), and the ETF/mutual-fund-only scope. No contradiction with 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?

Every sentence earns its place: a scoped purpose sentence, four actionable usage bullets, a compact section-options list, an exclusion with a named alternative, and a source/auth note. Information is front-loaded and scannable for an agent.

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 need not be spelled out, and annotations cover the safety profile. The description supplies scope, when-to-use triggers, section semantics, data source, and auth requirements. Minor gaps: no behavior specified for invalid symbols, and the fixed-income-only nature of bond_ratings is only implied rather than stated.

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?

With schema description coverage at 0% per context signals, the description carries the documentation burden and does compensate for the most important parameter: it lists all section options with their meanings and maps them to use cases in the bullets. However, it leaves symbol formatting to the schema and does not clarify the purpose of the auxiliary wrapper params (source_resource_id, wholesaler_ids, etc.), which appear irrelevant to a Yahoo Finance-backed fetch.

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 states a specific verb and resource — 'Fetch ETF or mutual fund specific data' — and enumerates the exact data areas returned (top holdings with weight %, sector allocations, expense ratio, bond credit quality ratings, equity style characteristics). It differentiates from siblings by naming the alternative: 'For stocks, use GetTickerInfo,' and its content list distinguishes it from overlapping tools like GetFundFees and GetHolders.

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?

Provides an explicit 'Use this tool when' list with four concrete trigger scenarios, from needing top-10 holdings with weights to comparing fund profiles for advisor recommendations. It also states a clear exclusion and routes to the alternative: 'Only works for ETFs and mutual funds. For stocks, use GetTickerInfo.'

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