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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description's job is to add context — and it does, disclosing the exact payload shape (phase per condition, trial/label backing, first approval year, targets, synonyms, cross-ref IDs) and that unii takes precedence over name. No auth or rate-limit notes, but for a read-only lookup that is minor.

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 purpose, then the returned payload, then example queries — no filler sentences. It is dense and long, but every clause carries specific information about what the tool returns.

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 full burden of explaining return values and does so thoroughly (per-condition phase, trial/label provenance, overall highest event, targets with potency, synonyms, cross-refs). An agent can call this and interpret the result without further documentation.

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% and both parameters are documented in the schema, including the unii-takes-precedence rule and the 10-character format. The description only restates 'by name or FDA UNII', adding no syntax or format detail beyond the schema, so the baseline 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+resource: 'Drug development status by indication ... for one drug or substance (by name or FDA UNII)', with the source system named. It implicitly but clearly distinguishes itself from the sibling inxight_indication by framing the lookup as drug→indications rather than indication→drugs.

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?

Three concrete trigger questions ('what is psilocybin being developed for and how far along', 'which indications is this drug approved for', 'is this compound still in trials') make the intended use unambiguous. It stops short of explicitly naming the inverse sibling inxight_indication or stating exclusions, so not a 5.

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