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

Goes well beyond the readOnly/openWorld/idempotent annotations: it discloses the exact price, that an unknown ticker returns 404 and is not charged, that a missing payment yields a 402 challenge, that failed calls after settlement charge nothing, and that the payment header is forwarded out-of-band. This is unusually rich behavioral disclosure for a paid endpoint.

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?

Dense and front-loaded with the paid notice and purpose before enumerating return fields and payment mechanics. Every sentence carries information, though the single long paragraph could be broken up for faster scanning.

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 an output schema present, return values need not be re-explained; the description still covers pricing, error/charging behavior, the 402 flow, filtering, and input format. Nothing an agent needs to call it correctly is missing.

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 already 100%, so the baseline is 3, but the description adds meaning beyond the schema: concrete form-type examples (10-K, 10-Q, 8-K, 4, DEF 14A), the 'newest first' ordering implied for limit, and the full semantics of the payment envelope. That extra context lifts it above the schema-only baseline.

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 ('latest SEC filings from EDGAR') with the input key (ticker or CIK), and enumerates the returned fields (form type, dates, accession number, 8-K item codes, sec.gov link, company metadata). No sibling tool covers SEC filings, so this is unambiguously distinct from the crypto/on-chain siblings.

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?

Explains how to invoke: provide ticker/CIK, optionally filter by form types, and how the two-call payment flow works (omit payment first, pay from the 402 challenge, or let fiatdock-mcp auto-pay). It does not need to route to an alternative since no sibling overlaps, but it also doesn't state when *not* to use it.

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