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

Annotations already carry readOnly, idempotent, non-destructive and closed-world hints, so the safety profile is fully covered. The description adds one genuinely new trait, 'each labelled by origin' (provenance attribution), but says nothing about failure behavior for unrecognized peptides or about depth/length of the result.

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?

A single tight sentence with the operation front-loaded and the compared fields enumerated in a readable list. Every clause carries information; no 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 enumerates the fields returned and their provenance labelling, which is exactly what an agent needs to know before calling. The remaining gap is the absent handling of unknown or ambiguous peptide names.

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%, with both `a` and `b` documented and exemplified, so the description's examples (semaglutide vs tirzepatide) largely duplicate them. It adds only the implicit constraint that exactly two items are compared, with no note on whether order matters or blends are allowed beyond the schema example.

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 (side-by-side comparison) and resource (two peptides) plus the comparison axes it covers: evidence, FDA status, half-life, routes, vial sizes, storage, dose ranges. It is clearly distinguishable from single-item tools like peptide_lookup or peptide_search, though it never names those siblings explicitly.

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?

Usage is implied by 'comparison of two peptides' and the worked examples, so an agent can infer this is the tool for head-to-head questions. There is no explicit when-to-use/when-not or routing to peptide_lookup for single-peptide questions, and no guidance on what happens when a name is not found.

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