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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely useful context in 'slim fields' (a reduced projection) and 'cursor pagination', plus a cost note '(free)'. It doesn't explain what slim fields include, the default page size, or whether this differs from get_peptide in what it returns.

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, front-loaded with the purpose, then the return shape and pagination, then the cost tier. There is no filler and nothing is buried.

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 simple read-only list tool with full schema coverage and annotations, this is nearly complete: purpose, pagination, and output breadth are all addressed. The one gap is that 'slim fields' is undefined and there is no output schema, so an agent cannot know exactly which fields come back or how this differs from get_peptide.

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%, with each of the five parameters documented, including q, limit range, cursor source, status example, and the body_system reference. The description only echoes filtering and cursor pagination at a high level and adds no format or behavioral detail beyond the schema, 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?

States a specific verb and resource: 'List and filter peptides', which is clearly a collection endpoint. It does not differentiate itself from siblings such as search or get_peptide, so an agent could not confidently choose it over search without opening the schema.

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 use this tool versus search, get_peptide, or compare_peptides is given. Usage is only implied by 'list and filter'; there are no exclusions or named alternatives.

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