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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. Beyond that, the description discloses the paid-access model ('$0.05 USDC per successful call via x402 (Base or Solana)') and the match resolution behavior — both non-obvious operational facts an agent needs before calling.

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 payload fields are front-loaded after the identifier clause, and the pricing caveat is a short trailing sentence. The field enumeration is long but each item is informative rather than filler; nothing is redundant with the schema.

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 burden of describing returns and does so thoroughly (tickers, EIN, incorporation, financials, Form D people and amount, recent filings). Payment model is disclosed. Minor gaps remain around error/no-match behavior and whether results are paginated.

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 100% for the single query parameter, so the baseline is 3. The description adds genuine semantics on top: it accepts name, ticker or CIK, and clarifies that a name query resolves to a best match plus additional matches, which affects how the agent should interpret results.

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?

Names the resource precisely ('A US company that files with the SEC') and the three accepted identifier types, then enumerates the returned data, so an agent knows exactly what this tool yields. The 'US' qualifier implicitly separates it from uk_company_lookup in the sibling list, but no sibling is named 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?

Usage is implied by the resource described (use this for SEC-filing US companies), and 'A name returns the best match plus other matches' tells the agent how to interpret a fuzzy query. There is no explicit when-not-to-use or named alternative (e.g., uk_company_lookup for UK entities, or which tool to use for officers).

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