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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds real behavioral value beyond that: the 4-year annual / 4-quarter quarterly data window, that results are transposed so each row is a reporting period, the Yahoo Finance/yfinance source, and that no API key is needed. It omits error/missing-symbol behavior, which keeps it from a 5.

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 the purpose, then trigger bullets, then option values, then provenance — a sensible order. The bullets are somewhat redundant with the opening sentence and the statement/freq options largely restate schema descriptions, but nothing is genuinely wasteful.

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-format explanation is unnecessary; the description covers what remains: data windows, row orientation, source, and option semantics. An agent has enough to call it correctly without opening the schema.

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 spells out the meaningful enum values ('income', 'cashflow', 'balance'; 'yearly', 'quarterly', 'trailing') and adds the notable constraint that TTM is income-only. It says nothing about 'symbol' (which the description never explicitly instructs the agent to supply) nor about the unrelated internal-fin parameters (wholesaler_ids, source_resource_id, etc.) present in the schema, leaving a gap given the reported 0% schema description coverage.

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 ('Fetch income statement, cash flow statement, or balance sheet for a stock') and enumerates the three statement variants. Clearly distinguishable from siblings like GetEarningsHistory and GetPriceHistory, which cover different 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?

The 'Use this tool when' bullets give concrete trigger conditions (revenue, net income, EPS, operating margins, CapEx, FCF, assets/debt/equity, fundamental analysis). However, it never states when NOT to use it or names an alternative sibling (e.g., GetEarningsHistory for EPS surprises or GetTickerInfo for quote data), so the routing guidance is one-sided.

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