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

Annotations only declare readOnlyHint and openWorldHint, so cost and payment behavior must come from the description — and it delivers: $0.002 USDC per call over x402, failed calls cost nothing, omit `payment` to receive a quote and re-call, and a free tier of 3 calls/day without a wallet. This is genuinely additive context. It loses a point for not mentioning the result cap (limit max 40) or any rate/coverage limits on EDGAR data.

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 core capability and return contents, then a compact pricing/payment paragraph. Every sentence carries information. Minor redundancy with the schema ("Filter by form type" restates the `form` field description).

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 work of describing returns (profile fields plus filings with direct links), and it fully covers the non-obvious x402 payment handshake. Remaining gaps are the undocumented `limit` cap and `cik` format, which an agent must infer.

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 60%: `form`, `ticker`, and `payment` are documented in the schema, while `cik` and `limit` carry no description anywhere. The description adds practical meaning for ticker/CIK lookup, form filtering, and the payment handshake, but leaves `limit` (1-40) and CIK format unexplained. Adequate but with a clear gap.

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?

Specific verb+resource: "Look up a US public company in SEC EDGAR by ticker or CIK," followed by an explicit enumeration of returned fields (legal name, exchange, industry, state, fiscal year end) and filings (10-K, 10-Q, 8-K, Form 4) with direct links. It is unambiguous what the tool does. It stops short of 5 because it never distinguishes itself from near-neighbors like sec_financials, company_snapshot, or company_due_diligence.

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 concrete operational guidance for payment ("Call without `payment` to get a quote", first 3 calls/day free) and one filtering hint ("Filter by form type, e.g. only 10-Ks"). However it offers no when-to-use/when-not-to-use guidance relative to the many sibling lookup tools (sec_financials, company_snapshot, company_due_diligence). Usage is implied rather than scoped.

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