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

readOnlyHint=true already establishes this is a safe read, and the description adds the data-source/endpoint context (openFDA drug/label). It does not disclose return shape, rate limits, or result-shaping behavior, so it goes modestly beyond the annotation but not richly.

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 dense sentence that front-loads the verb and resource before the enumerated contents. Every clause earns its place, though the em-dash list makes it slightly run-on rather than crisp.

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 read-only, zero-required-parameter search tool with no output schema, the description usefully signals what the returned labels contain, which partially compensates for the missing output schema. It omits nothing essential for correct invocation, though return-format guidance is absent.

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%, so skip, sort, limit, and search are all documented in the schema itself, including Lucene syntax and range examples. The description adds nothing parameter-specific, making the baseline 3 correct.

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+resource ('Search Structured Product Labeling (SPL)') and spells out what SPL contains — indications, warnings, dosage, adverse reactions, interactions — which cleanly separates it from siblings like search_drug_ndc, search_drug_events, and search_drug_recalls. The openFDA endpoint reference anchors it further.

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?

It conveys what kind of data lives here, which implicitly tells an agent when to reach for it, but there is no explicit when-to-use vs. alternative or any exclusion guidance against the many sibling search_* tools. Usage is inferred, not stated.

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