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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely non-structured behavior: a free daily quota followed by a paywall ($0.02 USDC via x402, or 1 credit via X-API-KEY), which materially changes how an agent should budget calls. It stops short of describing empty-result or error behavior, keeping it out of the top band.

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: the returned data is front-loaded, and the billing caveat is parked in parentheses where it doesn't obstruct the core purpose. The field enumeration is dense but each item is substantive rather than 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 usefully doubles as a return-value summary by listing the data families returned. Combined with full parameter coverage and explicit annotations, an agent has enough to call it correctly; only the sibling-selection guidance 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?

Only one parameter and schema coverage is 100%, with 'slug' documented as 'Peptide slug', so the schema already carries the meaning. The description never mentions the slug input, but it doesn't need to; baseline 3 applies when structured data does the work.

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?

The description names a specific resource ('approval timeline') and enumerates the exact data sources returned (Drugs@FDA applications, DailyMed label set IDs, ChEMBL max phase, first-approval year, mechanism of action). This is far more concrete than a tautology. It doesn't explicitly contrast itself with close siblings like get_regulatory or get_dossier, so an agent still has to infer which regulatory-flavored tool to pick.

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?

There is no statement of when to use this tool versus get_regulatory, get_dossier, get_safety, or get_peptide_summary, all of which live in the same regulatory/approval neighborhood. The only conditional guidance is about billing (free daily allowance, then paid), which tells the agent nothing about tool selection.

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