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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description is not the sole source of the safety profile. It still adds material context annotations cannot: the free Basic tier vs paid tiers, the exact field set returned, and that sources/freshness are included. It does not cover auth requirements or failure behavior for an invalid organisationsnummer, which keeps it below 5.

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?

Two sentences, front-loaded with the core action and input provenance, followed by the tier/cost caveat and its alternative. Nothing is repeated from the title or schema and every clause carries selection-relevant information.

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?

An output schema exists, so return-value documentation is not required, yet the description still lists the returned fields and flags cost tiers — enough for correct invocation on a one-parameter read tool. It omits only edge-case behavior (unknown or malformed organisationsnummer), which is minor.

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% and the single parameter is already documented as 'an id from search: the organisationsnummer'. The description restates the same meaning (id from search, organisationsnummer) rather than adding format, validation, or normalization details. Baseline 3 is appropriate when the schema does the heavy lifting.

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 (fetch) and resource (register identity of one Swedish company), names the exact input source (the id returned by search, i.e. the organisationsnummer), and enumerates the returned fields. An agent can distinguish it from siblings like get_company or search without opening any schema.

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?

Gives the precondition for use (id must come from search) and explicitly routes paid capability to an alternative: 'Verified and Intelligence (VAT/F-tax, history, annual reports, signals) are paid via get_company.' That is an explicit when-to-use-this vs when-to-use-something-else rule.

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