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

Annotations cover read-only/open-world, but the description adds vital behavioral facts they don't: per-page size (20), pagination ceiling implied by the page schema, the exact return payload, and a pricing model ($0.002 USDC per successful call via x402, failures free). That pricing/auth detail is the key disclosure an agent needs before invoking.

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?

Front-loaded with the register identity and identifier formats, followed by the return payload and pricing. Every sentence carries distinct information 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?

With an output schema present, return-format exposition is optional, yet the description still summarizes the payload, plus pagination and cost/payment mechanics. Combined with annotations covering safety, this is complete for correct invocation.

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 value by reinforcing accepted identifier formats in the query parameter and stating '20 records per page,' which clarifies the page parameter's granularity. Region narrowing is echoed but not elaborated beyond the schema examples.

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 (search/register lookup) and resource (Russia's official EGRUL/EGRIP register from the Federal Tax Service), naming the regulator and the identifier types accepted. This clearly distinguishes it from the many other country-registry siblings such as b2b_brreg_norway_companies or gov_krs_poland.

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?

Implies usage through the identifier formats (INN 10/12 digits, OGRN 13, OGRNIP 15, Cyrillic name) and the region-narrowing hint, so an agent knows this is the tool for Russian entity lookups. It stops short of explicitly naming when NOT to use it or which sibling to prefer for cross-border work.

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