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

Annotations already mark this as read-only and idempotent, so the description adds useful behavior beyond them: it returns public educational units, existing content only, and warns that range arrays may be empty without a reviewed source. The medical disclaimer is also a meaningful extra behavioral note.

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?

Three concise sentences with no repetition. The primary behavior is front-loaded, followed by the compatibility caveat and the disclaimer, each earning 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?

For a single-parameter read-only tool with an output schema and strong annotations, the description covers the essential call intent, edge-case behavior around empty ranges, and the public-content scope. Nothing critical is missing.

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 slug parameter already has a clear example and length constraints. The description reinforces that the slug must be exact but does not add substantive semantic information beyond the schema.

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?

Description states a specific verb and resource: returns educational units and existing content for one exact biomarker slug. The phrase 'exact biomarker slug' clearly differentiates it from plural or search-based sibling tools.

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 implies this is for a single exact slug lookup, and the caveat about public range sources is useful. However, it never explicitly says when to prefer this over search_biomarkers or browse_biomarkers, or what to do if the slug is unknown.

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