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

Annotations already declare readOnly, idempotent, openWorld and non-destructive behavior, so the safety profile is covered. The description adds a genuinely non-structured behavioral trait: the billing model (free daily allowance, then $0.003 USDC per call via x402), which lets an agent reason about cost. It stops short of stating the response shape, but an output schema exists.

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 short sentences with no filler; the functional purpose is front-loaded and the pricing detail is relegated to second position. Sized appropriately for a single-parameter lookup.

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 values need not be described, and annotations carry the safety profile. However, the description omits any routing against the many sibling lookup tools and never states the output is an LEI record, leaving the agent to infer the tool's place in the family.

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?

With one parameter at 100% schema coverage, the baseline is 3, but the schema description is merely 'BIC' while the description clarifies that this means a 'SWIFT/BIC code'. That expansion adds real meaning about the identifier's origin beyond the structured field.

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 names a concrete mapping task — find which entity holds a given SWIFT/BIC code — which pairs with the title's 'LEI by BIC' to convey verb and resource. It is clear on its own but never explicitly says it returns an LEI, and it does not distinguish itself from close siblings such as gleif__by-isin or gleif__lookup.

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?

No guidance is given about when to use this tool versus alternatives like gleif__lookup, gleif__by-isin, or gleif__search. The only contextual information is pricing ('free within the daily allowance, then $0.003 USDC per call'), which is cost, not usage routing.

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