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

Annotations already cover read-only, idempotent, open-world and non-destructive behavior. The description goes beyond them by disclosing the exact-vs-substring resolution rule with match_type marking, and by explaining what is returned (authoritative HSA listing and infosearch URLs) and what is not (no indication text). This is useful behavioral context an agent cannot get from the annotations.

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 sentences, front-loaded with the core purpose before the field list and the indication caveat. The field enumeration is dense but each item earns its place by telling the agent what comes back; no filler.

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 return-value burden and does so by listing the returned fields and URLs and flagging the absence of indication text. It is nearly complete for a single-record fetch; it omits not-found/error behavior but nothing essential to calling it correctly.

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 baseline is 3. The description adds resolution semantics not present in the schema: exact licence match, exact-then-substring name matching, and a marked match_type, which directly shapes how the parameters should be supplied.

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: 'The full HSA registration record for one Singapore therapeutic product'. It names the two lookup keys (SIN licence number or product name) and enumerates the record's fields, so an agent can distinguish it from the hsa_sg_search sibling that returns listings.

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 explains the lookup resolution order (exact name, else substring with match_type marked), which guides parameter use, but never explicitly says when to choose this over hsa_sg_search or hsa_sg_recent_changes. Usage is implied by 'for one ... product', with no named alternatives or exclusions.

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