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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuine behavioural context by disclosing that results are binned per rule property and split at a chosen rule's bound, but it says nothing about cost or limits on large libraries, nor about what happens when rules/alert_sets are empty (that only appears in the 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?

A single dense sentence that front-loads the screening action before the binning detail, with no wasted clauses. The one weak element is the parenthetical comparison 'as the library grid does', which spends words on an undefined reference.

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?

The presence of an output schema means return values need no explanation, and the read-only annotations cover safety. However, for an 8-parameter tool with nested _subject/_files structures, the description never indicates how the library is supplied (molecules array vs project record references), leaving a meaningful gap for a complex input surface.

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%, including per-value enum documentation for property, split_rule and the rule/alert catalogs, so the schema already carries the parameter burden. The description restates the property/split_rule relationship ('bin one rule property ... split at the bound of a chosen rule') but that interaction is also spelled out in the split_rule schema text, so it adds little beyond the baseline.

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 names a specific verb ('screen') and resource ('every structure of a library'), and adds the secondary operation of binning one rule property. It is clearly distinct from single-molecule siblings like assess_small_molecule or compare_molecules, but it never names a sibling to contrast with, and the phrase 'as the library grid does' is opaque to an agent that has no grid context.

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?

Usage is only implied by the phrase 'every structure of a library at once', which suggests bulk screening, but there is no explicit when-to-use or when-not-to-use guidance. Nothing routes the agent between this tool and near neighbours such as search_molecule_library, cluster_molecules, map_chemical_space, or assess_small_molecule.

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