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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds genuinely non-obvious behavioral context beyond them: a free daily allowance followed by metered pricing ($0.02 USDC via x402 or 1 credit with X-API-KEY). It stops short of describing coverage, depth, or response shape, but the cost/quota disclosure is exactly the kind of trait annotations cannot convey.

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 short sentences with the purpose front-loaded and no filler. The billing parenthetical is boilerplate shared across the server's tools, which slightly dilutes but does not derail it.

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 one-parameter read-only tool with full schema coverage and no output schema, the description is minimally sufficient, but it leaves the agent guessing how this differs from the other safety-adjacent siblings and what the notes actually contain. A single disambiguating clause would close the gap.

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 coverage is 100% and there is a single required parameter ('slug', documented as 'Peptide slug'), so the schema carries the semantics. The description adds nothing about the slug (e.g., format, lookup behavior on unknown slugs), so 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?

The description names a specific content domain (safety, toxicology, pharmacokinetics notes) that is distinguishable from siblings like get_adverse_events and get_regulatory, but it is a bare noun phrase with no verb stating that it retrieves notes for a given peptide. An agent can infer the resource but not the operation from the text alone.

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_adverse_events, get_regulatory, get_dossier, or get_peptide_summary, all of which could plausibly overlap with safety data. The only conditional content is billing, not selection guidance.

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