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

No annotations are provided, so the description must carry the behavioral burden, and it does disclose notable traits: cost ($0.25 USDC), the upstream data source, that registry-code matching is exact while name matching is fuzzy autocomplete, and the fields returned (legal name, status, address, historical names). It still omits payment/auth mechanics and what happens when a name search returns multiple or zero matches.

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 dense and front-loaded: purpose, source, key semantics, return fields, then concrete examples and price. The only mild friction is the juxtaposition of 'free, no contract' with '$0.25 USDC', which costs a moment of parsing.

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?

It usefully enumerates return fields even though no output schema exists, and covers the two primary lookup modes. But for a 7-parameter tool with no annotations and no schema documentation, the unexplained alias parameters (q, ee, number, reg_code) and absent multi-result/error behavior leave real gaps.

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 0% across 7 parameters, so the description must compensate, but it only explains registry_code and name (with concrete examples). The aliases reg_code, q, ee, and number are left entirely undefined, and limit is only inferable from its name, leaving most of the surface ambiguous.

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 (Estonian company lookup), names the authoritative source (äriregister autocomplete), and gives the two lookup keys (8-digit registry code exact match, or name). It is clearly distinguishable from the country siblings such as uk_company or fi_company.

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 tells the agent which inputs select which mode (registry_code for exact match, name for search) and notes it is free with no contract, which implies a low-friction first choice. However it never names alternatives or exclusions — nothing about when to prefer company_full, company_research, kyb_report, or registry_batch over this single-country lookup.

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