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

Annotations already declare readOnlyHint=true and openWorldHint=true. The description adds behavioral context beyond annotations: it describes the return format (dict with company name, status, address), error handling (returns error message if not found or API unavailable), and external API dependency. This is valuable additional transparency.

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 well-structured and front-loaded: purpose first, then usage guidelines, then parameter details with examples, then return format. Every sentence adds value, no wasted words. It is concise yet comprehensive.

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?

Given the moderate complexity (three country-specific formats, error handling) and the presence of an output schema (though not shown), the description covers the essential aspects. It explains inputs, outputs, and error cases. A slight improvement could be to mention that the output schema exists or provide more detail on the returned fields, but it is already complete enough for correct usage.

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 schema already documents both parameters. The description adds significant value by providing format examples per country (NO: 9 digits, DK: 8 digits CVR, FI: business ID with hyphen) and specifying the default for country. This helps the agent construct correct parameter values.

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?

The description clearly states the tool looks up a company in official business registries for Norway, Denmark, or Finland. It specifies the verb 'Look up' and resource 'company in official business registry'. It distinguishes from siblings by explicitly stating not to use for Sweden (use search_filings) and not for tickers/ISIN (use search_filings).

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 explicitly provides when-to-use (retrieve authoritative registration data for known organisation numbers) and when-not-to-use (for Sweden, for tickers/ISIN). It gives concrete alternatives: use search_filings with country='SE' for Sweden and search_filings for tickers/ISIN. This leaves no ambiguity.

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