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

Annotations already declare readOnly, idempotent, open-world, non-destructive behavior. The description adds value beyond them: keyless access, CC0 data provenance, and the important edge-case disclosure that unregistered relationships return 'none reported' rather than an error. It stops short of covering rate limits or failure modes, so 4.

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?

Four dense sentences, front-loaded with the source and output shape, no filler. Minor redundancy in the parenthetical 'keyless, CC0 open data' and the drill-down note slightly dilutes it, but it is efficient overall.

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 output schema, the description carries the full return-shape burden and does so: it names each returned field (LEI, legal name, jurisdiction), the relationship fields, the subsidiary count, and the exception semantics. An agent can call this correctly with no other reference.

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% — both query (name or 20-char LEI, top-ranked match) and children_limit (default 15, max 50, total always reported) are fully documented in the schema. The description adds no syntax or constraint detail beyond that, 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?

States a specific verb and resource (maps a corporate family tree from the GLEIF relationship register) and precisely enumerates the return set: direct parent, ultimate parent, children, total count. It does not, however, differentiate itself from close siblings like corporate_ownership_tree or beneficiary-ownership tools, so it falls short of a 5.

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 clear usage context by framing the questions it answers ('who ultimately owns this company?', 'what does this company own?') and tagging them as due-diligence/beneficial-ownership work. There are no explicit exclusions or named alternatives, so it stops at a solid 4.

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