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

Annotations already declare readOnlyHint=true and openWorldHint=true. The description adds valuable context beyond that: pricing model ($0.002 USDC per successful call via x402, failed calls not charged), data source (eCFR), search limitation (only table entries, not paragraph entries), and result cap (up to 20 matches per call). This is a solid behavioral disclosure, though it stops short of describing return values or pagination behavior (which the output schema presumably covers).

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?

The description is a single dense sentence with semicolons, front-loaded with purpose and scope. Every clause earns its place: data source, return fields, search limitations, exclusions, result cap, and pricing. It is efficient, though slightly crammed and could be marginally more readable with sentence breaks.

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?

Given the tool's complexity (a read-only lookup with a complete input schema, output schema, and annotations), the description covers the essential context: what it returns, what it excludes, data source, result cap, and cost. Nothing critical is missing for an agent to call it correctly.

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 both parameters are fully documented in the schema. The description adds a small amount of context ('matching a name' and 'Up to 20 matches per call' relating to the max parameter), but does not meaningfully extend parameter semantics beyond what the schema provides. Baseline 3 is appropriate.

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 states a specific verb (returns/lookup) and resource (DEA controlled substance schedules, 21 CFR 1308.11-1308.15), and specifies exactly what data is returned: substance name and DEA Controlled Substances Code Number for schedule I–V table entries matching a name. It distinguishes from siblings because no sibling covers DEA controlled substances.

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 gives useful scope limitations (e.g., 'Substances listed only in paragraphs are not searched' and 'Does not include registration status'), which help an agent understand when the tool will not work. However, it does not explicitly say when to use this tool versus alternatives, nor does it name any alternative tools.

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