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

Annotations already establish read-only, idempotent, non-destructive behavior, and the description adds valuable semantics beyond that: results are broken down by species and tissue, include functional class and JECFA evaluations, and an empty limit list is meaningful rather than an error. The chloramphenicol example explicitly warns about substances with no Codex MRL, which is exactly the kind of edge-case behavior an agent needs.

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 front-loaded with the core action and output structure in the first sentence, followed by the input form and a meaningful empty-list caveat. It is slightly dense but every sentence earns its place; only minor redundancy exists in repeating the 'name or numeric id' contract already present in the schema.

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 tool with one required parameter and no output schema, the description covers the input form, the result structure, and an important empty-result interpretation. It omits only minor practical context such as where numeric ids come from or how to discover drug names through the sibling search tool.

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?

The schema already documents the single 'drug' parameter at 100% coverage, including type, example, and the 'name or numeric id' format. The description repeats this contract without adding new parameter-specific details, so with high schema coverage the baseline of 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 opens with a specific verb and resource: 'Get the Codex maximum residue limits for one veterinary drug,' and further specifies the output breakdown by species/tissue, functional class, and JECFA evaluations. This differentiates it clearly from sibling tools like codex_pesticide_mrls and codex_commodity_mrls by naming the veterinary-drug scope.

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 provides clear usage context: this is a single-drug lookup tool that 'Accepts a drug name or numeric id,' which implies it is not a search or comparison tool. However, it does not explicitly name alternatives like codex_vetdrug_search or state when not to use this tool, so the guidance is clear but not fully explicit.

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