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

Annotations already cover read-only and open-world behavior, yet the description adds genuinely useful operational context: a per-call price of $0.002 USDC via x402 with named payment chains, and the fact that failed calls are not charged. It also flags that results are rule text, not a legal opinion, setting expectations for output interpretation; only pagination/format behavior is left to the output schema.

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?

Front-loads the substantive answer (what the tool returns and from which source) before the caveats and pricing. Two sentences, both earning their place, though the first is a long noun phrase rather than a crisp verb statement.

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 two-optional-parameter read tool with an output schema and annotations, the description covers source, scope, exclusions, cost, and result caveats. The only gap is sibling differentiation within the dense hazmat cluster, which leaves an agent to infer which of several dangerous-goods tools to pick.

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?

With schema coverage at 100%, both limit (1-10, default 3) and keyword (3-40 chars, default 'aircraft') are already documented in the schema. The description reinforces keyword usage with examples but adds nothing about limit bounds or behavior, so the 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?

Names a specific resource (paragraphs of 49 CFR 173.185, the US lithium-battery hazmat rule from eCFR) and the retrieval condition (paragraphs that mention a keyword). It also explicitly excludes the IATA DGR, which is the most likely confusion point for an agent choosing among hazmat siblings.

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?

Gives clear context: use this for the US rule text, not the paid IATA regulations, and offers sample keywords ('aircraft', 'UN3480') that show the intended query style. It stops short of routing against near neighbors like logistics_un_dangerous_goods or logistics_hazardous_placard_id, so the alternative-selection guidance is incomplete.

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