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

With no annotations, the description carries the full burden, and it does add real value beyond the schema: the upstream source/API (PRH open data v3), the CC BY 4.0 license, and a per-call price of 0.01 USD via x402. However, it omits failure/empty-result behavior, whether name matching is fuzzy or exact, and any rate limit or retry characteristics.

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 front-loaded sentence that leads with the resource and lookup keys before listing return fields and licensing/price. Dense but every clause carries information; a slight readability cost from cramming attribution and pricing into the same sentence.

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 no annotations and no output schema, the description usefully enumerates the returned fields and the pricing/licensing context, which is what an agent needs before spending money. The remaining gap is the zero-required-parameter situation: it implies one identifier must be supplied but never states that explicitly or what happens if neither is given.

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 both parameters including the example ID format. The description only restates that lookup can happen by Business ID or name and adds no precedence rule, no guidance on combining the two, and no detail on what the up-to-5 name candidates look like.

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?

Names a specific verb (lookup) and a precise resource (Finnish company in the official YTJ/PRH register), enumerates the lookup keys (Business ID or name) and the returned data categories (names, legal form, address, industry, registration date, liquidation/bankruptcy). The contrast with the sibling no_company (Norwegian) is implicit but obvious from 'Finnish'.

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?

Usage is only implied: an agent can infer this is the tool for Finnish company data, and the schema hints that name search returns up to 5 candidates while businessId is exact. There is no explicit when-to-use, no routing guidance versus no_company or lei_lookup, and no statement about which key to prefer or whether both may be supplied.

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