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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuine value by disclosing the return shape (UNII and class, total hit count, breakdowns by status/phase/top conditions), which goes beyond what the annotations provide.

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 with the core action, and the enum list and usage guidance follow. Two dense sentences with little waste; the return-breakdown detail is slightly verbose but earns its place given there is no output schema.

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 correctly fills the gap by describing return content and the downstream consumer of the UNII. Required param and the limit/offset defaults are handled by the schema, so nothing critical 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 description coverage is 100% (baseline 3), and the description still adds meaning: it spells out the free-text matchable fields and enumerates the six development_status values inline. This clarifies the semantics of the two most important params beyond the schema text.

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 ('Search NCATS Inxight Drugs substances by free text') and immediately scopes what the free text matches (drug name, synonym, code, company or condition words). Readily distinguishable from the inxight_substance and inxight_indication siblings.

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?

Gives concrete usage context: 'find the UNII to pass to inxight_substance' and 'scan, e.g., which psychedelics are in clinical development', which names the downstream sibling. No explicit when-not-to-use or exclusion criteria, but the routing intent is clear.

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