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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: the cost per call ($0.005), the payment-required error for unpaid calls, the newest-first ordering, and the direct sec.gov document_url. It does not describe pagination or rate limits, but the output schema likely covers the return shape. No contradiction with 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 compact and front-loaded: the first sentence states what the tool returns and the ordering; the second sentence gives usage guidance and alternatives; the third sentence discloses cost and error behavior. Every sentence earns its place, and the cost/error note is placed at the end where it doesn't obscure the primary purpose.

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?

For a read-only, idempotent list tool with a rich output schema and 100% parameter documentation, the description is complete. It covers what the tool returns, how to use it, when to use alternatives, how to resolve a ticker to a CIK, and the cost/error condition. An agent has everything needed to select and invoke this tool correctly.

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 100%, so the schema already documents all three parameters. The description adds meaning beyond the schema by explaining the purpose of the returned fields (form, filing date, report period, accession number, 8-K item codes, document_url) and by clarifying the 'form' parameter's SEC naming convention with examples. The cik parameter description also adds a practical routing hint to lookup_company. This exceeds the baseline 3 for full schema coverage.

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 states a specific verb ('find or cite'), a precise resource ('SEC filing index for one company'), and the exact output fields (form, filing date, report period, accession number, 8-K item codes, document_url). It also names the sibling tools it is not (company_facts, company_financials), so an agent can distinguish it from the other company_* tools without opening schemas.

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 when to use this tool ('to find or cite a specific 10-K, 10-Q, 8-K or Form 4') and when to use alternatives ('use company_facts or company_financials for the numbers in the filings'). It also gives a concrete routing hint in the cik parameter description ('Only have a ticker or company name? Call lookup_company first'). This is explicit when/when-not guidance.

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