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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), and the description adds substantial behavior beyond them: provenance per figure (XBRL concept, filing, date), how figures were derived (filed, reconstructed from year-to-date, computed from named lines), restatement handling with the earlier value retained, and the explicit-null-never-carried-forward rule. It also discloses the refusal mode and its cost consequence and the x402 billing/free-cache mechanics.

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 capability, scope and return shape are front-loaded in the first sentence, with provenance rules, filing index, refusal mode and pricing following in a logical order. Dense but nearly every clause carries distinct information; the pricing/legal disclaimer sentences are the closest to padding, keeping it short of a 5.

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 full burden of describing returns and does so thoroughly: statement coverage, period count, provenance metadata, derivation flags, restatement and null semantics, plus the filing index contents. Combined with the refusal and payment behavior, an agent has everything needed to call and interpret this tool.

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% for both parameters, so the schema already documents the ticker format and the x_payment challenge/retry flow. The description adds no ticker syntax or payment-format detail beyond what the schema states, so the baseline of 3 applies.

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 ('Read the SEC statement set for a US-listed company') and enumerates exactly what is returned: income statement, balance sheet, cash flow, up to five fiscal periods, annual and quarterly, plus the 10-K/10-Q/8-K filing index. An agent can tell this apart from sibling tools such as otto_equity_intel or otto_material_events without opening any 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?

The description gives eligibility context (a fund vehicle or non-USD-only filer is refused as `not_applicable`, nothing charged) and the payment path (first eligible cached result is free, otherwise $0.003 USDC via x402), which is useful operational guidance. However it never names an alternative tool or states when to prefer this over otto_equity_intel, otto_catalog, or other sibling research tools; usage is implied from the topic rather than routed.

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