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

The annotations already mark the tool as read-only and non-destructive, and the description adds meaningful behavioral detail beyond that: it returns latest-restated values, targets one exact period end, derives discrete quarterly flow rows from cumulative YTD values when necessary, and marks those rows as Derived. This gives the agent a clear picture of what the tool actually does at runtime.

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 longer than average but every sentence earns its place: scope, output behavior, derived-quarter caveat, and sibling routing are all covered without redundancy. It is front-loaded with the core purpose and then layers in necessary constraint details.

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 no output schema, the description carries the responsibility for explaining return semantics, and it does so: standard line items, latest-restated value, one exact period end, discrete quarterly rows, and the Derived flag are all disclosed. It also covers source provenance, exclusions, and alternatives, making it complete for an agent to select and invoke this tool 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 the description is not burdened with compensating for undocumented parameters. It restates the statement types and period concept already covered by the schema, and the Q4 caveat is already present in the period parameter description. It adds little parameter-level meaning beyond the structured schema.

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 names a specific action and resource: get a company's income statement, balance sheet, or cash-flow statement for a fiscal year and period. It also differentiates itself from siblings by explicitly excluding dimensional facts and naming GetRevenueBreakdown, GetFinancialFact, and CompareFinancialFact as the alternatives for those cases.

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 description gives explicit when-to-use guidance, including the note that most filers do not report discrete Q4 income/cash-flow facts and that 'FY' should be used for annual figures. It also tells the agent exactly when to prefer sibling tools such as GetRevenueBreakdown and GetFinancialFact.

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