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

Goes well past readOnlyHint/openWorldHint: names the data source and its public-domain status, the one-day cache and trimming, the 10-result cap with prefix-first ordering, the 404 failure mode, and the pricing/payment model (x402, $0.002 USDC per successful call on Base/Solana/Arc, failed calls uncharged). Payment mechanics and failure costing are exactly the kind of pre-invocation context an agent needs.

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?

Three tight sentences, front-loaded with the mapping behavior and then the operational facts. Dense but each clause carries information; the cache/timing detail is the only piece that sits near the edge of necessity.

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?

Output schema exists, so return values need no explanation. Inputs, match limits, source and coverage boundary, failure semantics, and cost are all present — nothing an agent needs before calling this 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 100%, so the baseline is 3; the description adds value beyond it by clarifying that a name fragment yields up to 10 matches ordered with prefix hits first, and by contrasting exact ticker/CIK matching against fragment matching. It does not add format details such as CIK padding or case sensitivity.

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 chain: maps a ticker / SEC CIK / name fragment to the other two plus the exchange. The scope qualifier 'Covers companies with an SEC ticker only' and the source ('SEC's company ticker file') distinguish it from siblings like company_registry, company_br/company_fr, lei and sec_search without the agent needing to open a schema.

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?

Explicit input forms (exact ticker, exact CIK, or name fragment of 3+ characters, up to 10 matches with prefix-first ordering) and an explicit exclusion ('Covers companies with an SEC ticker only', non-matches return 404). It stops short of naming which sibling to use for non-US or non-SEC-ticker companies, so routing outside the SEC universe is left to inference.

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