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

Beyond the readOnly/idempotent/openWorld annotations, the description discloses the critical behavioral facts: a cost of 0.01 USDC via x402 or 5 credits of an API key, and a free tier of the first 5 paid-tool calls per day with no payment or key. It also discloses the coverage boundary (no private companies), which prevents wasted paid calls.

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?

A single dense paragraph that is front-loaded with purpose, then constraints, then inputs, then pricing. Every clause carries information an agent needs — coverage limits, input modes, cost model, and free tier — with no filler.

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?

Because there is no output schema, the description properly enumerates what the record contains (legal name, former names, tickers/exchanges, EIN, incorporation state, industry code, address, latest 10-K/20-F and 10-Q dates), and payment mechanics are fully covered. The gap is that with zero required parameters, the description never says an identifier must be supplied, leaving a plausible zero-argument invocation unaddressed.

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 baseline is 3, but the description adds the meaningful routing detail that name, ticker or CIK are alternative inputs ("or"), and gives the same examples the schema does. It stops short of stating that at least one identifier is required, which matters because required parameters is 0.

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 (verify/find) and resource (US listed company or SEC registrant in EDGAR), and enumerates the record fields returned. The explicit scoping note that private US companies are not in EDGAR separates it cleanly from general lookup siblings such as company_lookup and the region-specific eu_company_check.

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?

"Use to verify a US listed company or SEC registrant" gives a clear when-to-use, and "Private US companies are not in EDGAR" supplies an explicit when-not. It does not name a specific sibling alternative for private-company cases, so routing relies on the agent inferring from the sibling list.

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