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

Annotations already declare readOnly, idempotent, and non-destructive hints, so the burden on the description is lighter. The description adds useful behavioral details: it returns filing and report dates, a direct sec.gov link, and notes that a ticker without SEC index entry returns NOT_FOUND as a non-billable result. It does not elaborate on pagination or result limits, but the output schema presumably covers the structure. This is strong beyond the annotations.

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 description is three sentences, front-loaded with the core function, then a usage guideline section, then pricing. Each sentence earns its place. It could drop the pricing line or move it to annotations, but it doesn't hurt clarity. Minor structural waste from the pricing sentence, which might be better as a note, but overall efficient.

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?

Given the tool's moderate complexity, 100% schema coverage, and presence of an output schema, the description covers all essential aspects: what it does, how to use parameters, when to use it, behavioral quirks (CIK normalization, NOT_FOUND non-billable), and limitations (no filer identity). The output schema presumably documents the return structure, so no need to repeat it. Complete for an agent to confidently select and invoke.

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%, so baseline is 3. The description adds meaningful context beyond the schema: it explains how CIK prefixes and leading zeros are handled, that tickers are matched case-insensitively, that company names are not accepted (pointing to company_us_resolve), and the default form list. The form parameter gets clarity on matching and ordering. The extra explanations elevate this to a 4.

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?

The description clearly states it retrieves the most recent EDGAR filings (10-K, 10-Q, 8-K) for a US company given a ticker or CIK, providing dates and direct sec.gov links. This is a specific verb+resource combination that distinguishes it from siblings like company_us_filings (which may retrieve historical filings) and company_us_resolve (which resolves company names).

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 explicitly says 'Use when: What is Apple's latest 8-K, and where is the document?' and provides a clear 'Not for:' case explaining that it doesn't return filer identity and unsuitable for ownership forms. This gives direct when-to-use and when-not-to-use guidance, and implicitly steers users toward siblings like company_us_profile for other needs.

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