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

Adds behavior beyond the annotations: it discloses a guard condition (refuses a target at or above the liver blood flow ceiling) and that the ceiling itself is returned on refusal. It also flags the accuracy caveat that the IVIVE is uncorrected with no error band, which is exactly the kind of domain limitation an agent cannot infer from readOnlyHint/idempotentHint.

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 tight sentences that front-load the core quantity before the sibling comparison and the edge-case behavior. The parenthetical 'e.g. to set a CLint cut-off for a screening cascade' is the only slightly expendable clause, but it earns its place as usage context.

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 7-parameter inverse-calculation tool with no output schema, it covers the failure mode, the return value on refusal, and the modeling caveat. What remains thin is how the model/assay_type choices interact with the returned units, but the schema largely carries that.

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%, so every parameter is already documented, and the description's mention of needing fu,mic and fu,p merely restates two required fields. It adds no meaning for rb, species, model, or assay_type beyond what the schema states, 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?

States a specific quantity (the in-vitro CLint an assay must read) and its purpose (reach a target plasma clearance in mL/min/kg), which is a concrete verb+resource framing. It explicitly positions itself as the inverse of the sibling calc_clhep, so an agent can distinguish the two without opening either schema.

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 a concrete use case (setting a CLint cut-off for a screening cascade) and frames the alternative relationship as 'calc_clhep run backwards', which implicitly routes forward-direction work to the sibling. It does not state explicit exclusions (e.g., when a target is unattainable for reasons other than the blood-flow ceiling), so it falls short of a full when/when-not statement.

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