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

Beyond the readOnly/non-destructive annotations, the description discloses two non-obvious traits: every row consumes credits, and a nightly update between pages may shift rows (explaining the non-idempotent hint). It does not cover failure modes for a malformed segment expression or how pagination terminates, so it is strong but not exhaustive.

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?

Three tight sentences, front-loaded with the action, that cover the required pairing, the continuation path, field defaults, cost, and the freshness caveat. No sentence is filler and the alternative tool is mentioned only where it changes the decision.

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 shape needn't be explained, and the description covers pagination, field selection, sorting limits, and cost. The one gap is that 'segment expression' syntax is never characterized — the agent must infer it from firmafakta_describe or firmafakta_load.

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 per, next, fields, sort, limit and segment are already documented in the schema with the same wording. The description's parameter commentary ('required with segment', 'without fields each row has describe's short_fields') largely restates the schema rather than adding new semantics, so the baseline 3 applies.

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 first sentence gives a specific verb and resource ('Fetch a page of a segment's rows'), and the body immediately distinguishes this from firmafakta_lookup ('for everything on one company'). It also defines what a row means per mode (workplace vs company with its main workplace), so an agent can tell it apart from siblings without opening schemas.

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?

It states the two mutually exclusive calling patterns explicitly: 'Pass segment and per ... or only next from the previous page to continue.' It also names the alternative for a different need ('use firmafakta_lookup for everything on one company') and routes field discovery to firmafakta_describe, leaving little to inference.

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