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

Annotations already declare readOnlyHint=true and idempotentHint=true, and the description adds substantial behavioral detail beyond that: it names the two registries queried, highlights that it returns an honest not_found with sources when absent, and mentions the free quota and pricing. This goes well beyond the annotation hints and gives the agent a clear model of how the tool behaves under all outcomes.

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 long but every sentence earns its place: purpose, registry sources, full return field list, non-fabrication guarantee, and cost model. It is front-loaded with the core action and immediately informs the agent of the most critical behavioral trait (honesty). No filler or redundancy.

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 that there is no output schema, the description compensates by listing every return field. It also covers failure behavior (not_found), sources queried, and cost. For a read-only lookup with simple parameters and clear behavior, nothing critical is missing – an agent has everything needed to correctly invoke and interpret the tool.

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 all three parameters. The description does not add any parameter-specific semantics beyond what the schema provides; it only implicitly references name and LEI in the context of the registry output. With full coverage, a baseline score of 3 is appropriate.

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 states a specific verb ('lookup'), a precise resource (official company registry records via GLEIF and SEC EDGAR), and enumerates the returned fields (legal name, LEI, status, jurisdiction, etc.). It also explicitly declares what it will never do ('never fabricates'), which distinguishes it from other tools by setting clear expectations.

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 does not explicitly name alternative tools or conditions for choosing this one, but the sibling list contains no similar lookup tools, so the absence of explicit exclusion is acceptable. The description does provide strong contextual cues about when it is appropriate: it is a free/live lookup with honest not_found behavior, which helps the agent decide to use it for authoritative registry queries. However, it stops short of stating 'use X instead' or 'do not use when Y'.

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