rcsb_get_nonpolymer_entities

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

Beyond annotations (read-only, idempotent, open-world), the description discloses the default field set, the behavior of unknown IDs ('returned under not_found'), and the fact that fields replaces the curated default. This adds meaningful behavioral context without contradicting annotations.

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 compact, front-loaded with the core purpose, and then structured into default fields, cross-tool guidance, and an Args section. Every sentence adds value; there is no repetition of schema or annotation info.

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 read-only nature, output schema presence, and sibling context, this description is complete: it covers what the tool returns by default, how to customize fields, what happens with bad IDs, and where to go for related chemistry data. No critical gap remains.

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 0%, but the description fully compensates: it explains entity_ids as 'entry + entity number' with an example, and fields as 'Optional GraphQL selection replacing the curated default' with an example and discovery path. Both parameters get actionable semantics.

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?

Description opens with 'Fetch non-polymer (ligand/cofactor) entities' – a specific verb and resource. It distinguishes itself from related sibling tools by explicitly naming the counterpart rcsb_get_chem_comps for component chemistry, and the term 'non-polymer' is a clear contrast to polymer/branched sibling entities.

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 tells the agent to use rcsb_get_chem_comps when the chemistry of the bound component is needed, and points to rcsb_describe_data_object for field path discovery. It does not explicitly state when to avoid this tool, but the alternative pointers give clear usage context.

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