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

With no annotations, the description carries the full burden and does so well: it discloses that matching is exact or fuzzy, that results include match_quality and an ambiguous flag, that candidate records carry status/competent authority/source URL, that ESMA attribution and register links are returned, and it adds a 60 calls/min per-client rate limit plus the negative-result caveat.

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?

Front-loaded as a question with the register variants in parentheses, then capabilities, then return shape, then caveat and rate limit. Dense but every sentence adds information; the parenthetical register list is the only mildly heavy element.

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?

For a read-only lookup with no output schema, the description supplies the return shape, the ambiguity/quality semantics, the negative-result interpretation and operational limits. Nothing an agent needs to call this correctly is missing.

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 coverage is 100%, so the baseline is 3. The description still adds value beyond the schema by specifying the matching behaviour ('exact or fuzzy'), the either/or relationship between name and ref (LEI), and that country narrows name matches only.

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?

Opens with a specific question ('Is this firm on the ESMA MiCA register') and enumerates the exact register variants it covers (CASP, e-money token issuer, white paper, non-compliant warning list). Combined with 'look up a firm ... by name ... or LEI', an agent knows the verb, the resource and the scope without opening the 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?

States the operating context clearly ('Free', per-client rate limit) and gives an important interpretive guardrail: 'Absence from the register is not clearance.' It does not name alternatives or exclusion cases, but the listed siblings (chain, corridor, provider lookups) are in unrelated domains, so the routing risk is low.

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