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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true), and the description adds real behavioral context beyond them: the x402 pricing model ($0.03 USDC per call), that failed calls are free, and the two-step quote-then-pay handshake. It omits latency or rate-limit behavior, but the payment mechanics are the significant disclosure here.

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 capability list, followed by a compact payment/cost line. Every sentence carries information; the only mild redundancy is the 'in one call' phrasing that recurs implicitly in the enumeration.

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 does the necessary work of enumerating return content (profile, ratios, filings with links, plain-English 8-K summaries), so an agent knows what comes back. Pricing and the payment handshake are covered; only the cik parameter's meaning is left to 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?

Schema coverage is 67%: ticker and payment are documented in the schema, cik is not. The description reinforces the payment parameter's intent by explaining the quote-first workflow, but adds nothing about cik's format (10-digit SEC identifier) or the ticker/cik mutual exclusivity beyond what the schema already says.

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 ('Run due diligence on a US public company') and enumerates exactly what the call returns: profile, growth, margins, leverage/cash ratios, filings, and 8-K summaries. The 'in one call' framing implicitly separates it from the narrower siblings sec_company and sec_financials, though it never names them explicitly.

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?

Gives clear operational guidance for the payment flow ('call without `payment` to get a quote'), but says nothing about when to pick this composite tool over sec_company, sec_financials, or company_snapshot, which appear to be the obvious alternatives. Usage is implied by scope rather than stated.

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