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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds valuable behavioral context: it enumerates the exact fields carried in each entry (grade, band, COA status, buy link, coupon, affiliate disclosure) and the sort order, which is not visible from the schema or annotations. This goes beyond the minimum bar.

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 with no filler. The first sentence states the action, scope, and sort. The second lists the included fields and the intended use. Every word earns its place.

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 must explain the return values, and it does thoroughly: it lists all data points carried in each entry (grade, band, COA status, buy link, coupon, affiliate disclosure). It also states the list is exhaustive ('every') which matches openWorldHint=false. The tool is simple, so this is complete.

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?

The tool has zero parameters, so the baseline is 4. The description's mention of sorting and entry composition provides semantic context about what the output reflects, but there are no parameters needing clarification. Overall, adequate.

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 opens with a specific verb ('List') and a clearly defined resource ('every PepEvolution-graded research-peptide vendor'). It also specifies the sort order (PepScore desc), which distinguishes it from siblings like check_vendor or find_peptide_sources that likely target individual vendors or broader source discovery.

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?

The description provides a clear use case ('Use to compare trusted peptide vendors at a glance'). It does not explicitly state when not to use this tool or name alternative sibling tools for other scenarios, so it misses the 'explicit alternatives' criterion for a 5.

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