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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, non-open-world), so the bar is lower. The description still adds real behavioral context: some fields may be withheld ('registered address (when shown publicly)') and an attribution obligation exists ('open-data attribution to include when presenting it'), which the agent would not otherwise know.

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?

A single sentence, front-loaded with verb, resource and key. It is dense with an enumerated field list, but nothing is wasted and the critical lookup key precedes the payload detail.

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 single-read tool with an output schema and full annotation coverage, the description is sufficient: it names the lookup key, flags conditionally-absent fields, and states the attribution requirement. Listing return fields is mildly redundant against the output schema but does not hurt.

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?

Only one parameter, and schema coverage is 100% with an inline example ('201108760R') and a regex pattern. The description's 'by its UEN' adds no syntax or format detail beyond the schema, so the baseline of 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 ('Get') and resource ('public registry record of one Singapore entity'), plus the lookup key (UEN). The singular 'one ... entity by its UEN' framing implicitly separates it from the search_companies sibling, so an agent can route correctly.

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?

Usage is only implied: the agent can infer it should use this when it already has a UEN. Neither search_companies nor any when-not condition (e.g. 'use search_companies if you only know the name') is named, so the alternative-routing guidance is left to inference.

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