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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the description's real contribution is the commercial model: a free daily allowance, then either $0.02 USDC via x402 or 1 credit with an X-API-KEY. That is genuinely useful pre-call context an agent cannot get from structured fields, though it says nothing about behavior when a peptide has no citations.

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 compact clauses with no filler; the core purpose leads and the billing parenthetical follows. The pricing clause is dense but every element earns its place by warning of cost.

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 lookup with no output schema this is close to sufficient, but it never indicates what a citation record contains (identifiers, source names, links) or what an empty result looks like. An agent can call it correctly but cannot predict the payload.

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 the single slug parameter is documented as 'Peptide slug', so the schema carries the load. The description's phrase 'for a peptide' confirms the mapping but adds no format, resolution, or fallback detail beyond it.

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?

Names a specific resource (source citations) bound to a specific entity (a peptide), which separates it from siblings like get_identifiers, get_dossier, or get_safety. It is a noun phrase rather than a verb+resource statement, but the intent is unambiguous.

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?

No guidance on when to prefer this over adjacent tools such as get_dossier or get_identifiers, and no statement of when citations are worth fetching versus other evidence tools. The only contextual detail given is billing, not selection logic.

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